Issue 1:
Reproducing code example:

See CI of gh-13441, gh-13463

Error message:

Four (separate) failures occurring in both of these PRs. I'm not sure if the failures are related, but I noticed them at the same time, so I'm putting them all here for now.

In Windows builds on Azure:

==============================================================================
Task : PowerShell
Description : Run a PowerShell script on Linux, macOS, or Windows
Version : 2.180.1
Author : Microsoft Corporation
Help : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/powershell
==============================================================================
Generating script.
========================== Starting Command Output ===========================
"C:\windows\System32\WindowsPowerShell\v1.0\powershell.exe" -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command ". 'D:\a\_temp\ca35efdd-7955-4298-a881-94018e1affc9.ps1'"
Traceback (most recent call last):
File "runtests.py", line 565, in <module>
main(argv=sys.argv[1:])
File "runtests.py", line 291, in main
__import__(PROJECT_MODULE)
ModuleNotFoundError: No module named 'scipy'
##[error]PowerShell exited with code '1'.
Finishing: Run SciPy Test Suite

In refguide_asv_check and Linux Tests we're seeing directed_hausdorff failures:

_________________________ TestHausdorff.test_symmetry __________________________
[gw0] linux -- Python 3.8.7 /opt/hostedtoolcache/Python/3.8.7/x64/bin/python
/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/scipy/spatial/tests/test_hausdorff.py:37: in test_symmetry
forward = directed_hausdorff(self.path_1, self.path_2)[0]
self = <scipy.spatial.tests.test_hausdorff.TestHausdorff object at 0x7f28fbea4970>
/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/scipy/spatial/distance.py:461: in directed_hausdorff
result = _hausdorff.directed_hausdorff(u, v, seed)
seed = 0
u = array([[ 0.35923135, 0.93324854, 0. ],
[-0.71983479, -0.69414542, 0. ],
[-0.92442618, ...0695034, 0. ],
[ 0.93629495, 0.3512147 , 0. ],
[-0.48493437, -0.87455055, 0. ]])
v = array([[ 1.18546344, 3.07972019, 0. ],
[-1.43966959, -1.38829085, 0. ],
[-1.84885236, ...1390068, 0. ],
[ 1.8725899 , 0.7024294 , 0. ],
[-0.96986874, -1.74910109, 0. ]])
_hausdorff.pyx:37: in scipy.spatial._hausdorff.directed_hausdorff
???
__all__ = ['directed_hausdorff']
__builtins__ = <builtins>
__doc__ = '\nDirected Hausdorff Code\n\n.. versionadded:: 0.19.0\n\n'
__file__ = '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/scipy/spatial/_hausdorff.cpython-38-x86_64-linux-gnu.so'
__loader__ = <_frozen_importlib_external.ExtensionFileLoader object at 0x7f2939a17490>
__name__ = 'scipy.spatial._hausdorff'
__package__ = 'scipy.spatial'
__pyx_unpickle_Enum = <built-in function __pyx_unpickle_Enum>
__spec__ = ModuleSpec(name='scipy.spatial._hausdorff', loader=<_frozen_importlib_external.ExtensionFileLoader object at 0x7f2939a.../hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/scipy/spatial/_hausdorff.cpython-38-x86_64-linux-gnu.so')
__test__ = {}
directed_hausdorff = <built-in function directed_hausdorff>
np = <module 'numpy' from '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/numpy/__init__.py'>
mtrand.pyx:4478: in numpy.random.mtrand.RandomState.shuffle
E UserWarning: `x` isn't a recognized object; `shuffle` is not guaranteed to behave correctly. E.g., non-numpy array/tensor objects with view semantics may contain duplicates after shuffling.
MutableSequence = <class 'collections.abc.MutableSequence'>
RandomState = <class 'numpy.random.mtrand.RandomState'>
_MT19937 = <class 'numpy.random._mt19937.MT19937'>
__all__ = ['beta', 'binomial', 'bytes', 'chisquare', 'choice', 'dirichlet', ...]
__builtins__ = <builtins>
__doc__ = None
__file__ = '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/numpy/random/mtrand.cpython-38-x86_64-linux-gnu.so'
__loader__ = <_frozen_importlib_external.ExtensionFileLoader object at 0x7f2942eb7d60>
__name__ = 'numpy.random.mtrand'
__package__ = 'numpy.random'
__spec__ = ModuleSpec(name='numpy.random.mtrand', loader=<_frozen_importlib_external.ExtensionFileLoader object at 0x7f2942eb7d60...'/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/numpy/random/mtrand.cpython-38-x86_64-linux-gnu.so')
__test__ = {'RandomState.binomial (line 3262)': '\n binomial(n, p, size=None)\n\n Draw samples from a binomial dist... array(['pooh', 'pooh', 'pooh', 'Christopher', 'piglet'], # random\n dtype='<U11')\n\n ", ...}
_rand = RandomState(MT19937) at 0x7F2943136E40
beta = <built-in method beta of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
binomial = <built-in method binomial of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
bytes = <built-in method bytes of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
chisquare = <built-in method chisquare of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
choice = <built-in method choice of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
dirichlet = <built-in method dirichlet of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
exponential = <built-in method exponential of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
f = <built-in method f of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
gamma = <built-in method gamma of numpy.random.mtrand.RandomState object at 0x7f2943136e40>

geometric = <built-in method geometric of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
get_state = <built-in method get_state of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
gumbel = <built-in method gumbel of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
hypergeometric = <built-in method hypergeometric of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
laplace = <built-in method laplace of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
logistic = <built-in method logistic of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
lognormal = <built-in method lognormal of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
logseries = <built-in method logseries of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
multinomial = <built-in method multinomial of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
multivariate_normal = <built-in method multivariate_normal of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
negative_binomial = <built-in method negative_binomial of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
noncentral_chisquare = <built-in method noncentral_chisquare of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
noncentral_f = <built-in method noncentral_f of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
normal = <built-in method normal of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
np = <module 'numpy' from '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/site-packages/numpy/__init__.py'>
operator = <module 'operator' from '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/operator.py'>
pareto = <built-in method pareto of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
permutation = <built-in method permutation of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
poisson = <built-in method poisson of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
power = <built-in method power of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
rand = <built-in method rand of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
randint = <built-in method randint of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
randn = <built-in method randn of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
random = <built-in method random of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
random_integers = <built-in method random_integers of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
random_sample = <built-in method random_sample of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
ranf = <built-in function ranf>
rayleigh = <built-in method rayleigh of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
seed = <built-in method seed of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
set_state = <built-in method set_state of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
shuffle = <built-in method shuffle of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
standard_cauchy = <built-in method standard_cauchy of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
standard_exponential = <built-in method standard_exponential of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
standard_gamma = <built-in method standard_gamma of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
standard_normal = <built-in method standard_normal of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
standard_t = <built-in method standard_t of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
triangular = <built-in method triangular of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
uniform = <built-in method uniform of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
vonmises = <built-in method vonmises of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
wald = <built-in method wald of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
warnings = <module 'warnings' from '/opt/hostedtoolcache/Python/3.8.7/x64/lib/python3.8/warnings.py'>
weibull = <built-in method weibull of numpy.random.mtrand.RandomState object at 0x7f2943136e40>
zipf = <built-in method zipf of numpy.random.mtrand.RandomState object at 0x7f2943136e40>

On AppVeyor:

C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-ev3j_zdy\build\temp.win-amd64-3.7\scipy\integrate\quadpack\dqwgtc.o C:\Use
rs\appveyor\AppData\Local\Temp\1\pip-req-build-ev3j_zdy\build\temp.win-amd64-3.7\scipy\integrate\quadpack\dqwgtf.o
C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-ev3j_zdy\build\temp.win-amd64-3.7\scipy\integrate\quadpack\dqwgts.o -LC:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\lib\gcc\x86_64-w64-mingw32\6.3.0
-Lc:\python37-x64\libs -Lc:\python37-x64\PCbuild\amd64 -Lbuild\temp.win-amd64-3.7 -o build\temp.win-amd64-3.7\Release\.libs\libdqag.QD7OX7SDRWGIZYWWAF2SE2SG6JDJXW3B.gfortran-win_amd64.dll
build\temp.win-amd64-3.7\Release\.libs\libopenblas.3HBPCJB5BPQGKWVZAVEBXNNJ2Q2G3TUP.gfortran-win_amd64.dll -Wl,--allow-multiple-definition
-Wl,--output-def,build\temp.win-amd64-3.7\Release\libdqag.QD7OX7SDRWGIZYWWAF2SE2SG6JDJXW3B.gfortran-win_amd64.def -Wl,--export-all-symbols -Wl,--enable-auto-import -static -mlong-double-64" failed with exit status 1
Building wheel for scipy (PEP 517): finished with status 'error'
ERROR: Failed building wheel for scipy
Failed to build scipy
ERROR: Failed to build one or more wheels
Exception information:
Traceback (most recent call last):
File "c:\python37-x64\lib\site-packages\pip\_internal\cli\base_command.py", line 189, in _main
status = self.run(options, args)
File "c:\python37-x64\lib\site-packages\pip\_internal\cli\req_command.py", line 178, in wrapper
return func(self, options, args)
File "c:\python37-x64\lib\site-packages\pip\_internal\commands\wheel.py", line 191, in run
"Failed to build one or more wheels"
pip._internal.exceptions.CommandError: Failed to build one or more wheels

I am also seeing this in macOS tests, but that might be unrelated, as I've seen it intermittently before today:

gcc: /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmp76pay1ja/source.c
gcc /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmp76pay1ja/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmp76pay1ja/source.o -L/usr/local/lib -lopenblas -o /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmp76pay1ja/a.out
FOUND:
libraries = ['openblas', 'openblas']
library_dirs = ['/usr/local/lib']
language = c
define_macros = [('HAVE_CBLAS', None)]
runtime_library_dirs = ['/usr/local/lib']

FOUND:
libraries = ['openblas', 'openblas']
library_dirs = ['/usr/local/lib']
language = c
define_macros = [('HAVE_CBLAS', None)]
runtime_library_dirs = ['/usr/local/lib']

/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py:936: UserWarning: Specified path /usr/local/include/python3.9 is invalid.
return self.get_paths(self.section, key)
blas_opt_info:
blas_mkl_info:
libraries mkl_rt not found in ['/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE

blis_info:
libraries blis not found in ['/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE

openblas_info:
C compiler: gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -I/usr/local/opt/sqlite/include -I/usr/local/opt/sqlite/include

creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var
creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders
creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders/24
creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn
creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T
creating /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b
compile options: '-c'
gcc: /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/source.c
gcc /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/source.o -L/usr/local/lib -lopenblas -o /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tmpayy_ek6b/a.out
FOUND:
libraries = ['openblas', 'openblas']
library_dirs = ['/usr/local/lib']
language = c
define_macros = [('HAVE_CBLAS', None)]
runtime_library_dirs = ['/usr/local/lib']

FOUND:
libraries = ['openblas', 'openblas']
library_dirs = ['/usr/local/lib']
language = c
define_macros = [('HAVE_CBLAS', None)]
runtime_library_dirs = ['/usr/local/lib']

blas_info:
Traceback (most recent call last):
File "/Users/runner/work/scipy/scipy/setup.py", line 605, in <module>
setup_package()
File "/Users/runner/work/scipy/scipy/setup.py", line 601, in setup_package
setup(**metadata)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/core.py", line 135, in setup
config = configuration()
File "/Users/runner/work/scipy/scipy/setup.py", line 524, in configuration
config.add_subpackage('scipy')
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 1019, in add_subpackage
config_list = self.get_subpackage(subpackage_name, subpackage_path,
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 985, in get_subpackage
config = self._get_configuration_from_setup_py(
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 927, in _get_configuration_from_setup_py
config = setup_module.configuration(*args)
File "scipy/setup.py", line 18, in configuration
config.add_subpackage('optimize')
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 1019, in add_subpackage
config_list = self.get_subpackage(subpackage_name, subpackage_path,
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 985, in get_subpackage
config = self._get_configuration_from_setup_py(
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/misc_util.py", line 927, in _get_configuration_from_setup_py
config = setup_module.configuration(*args)
File "scipy/optimize/setup.py", line 102, in configuration
ext = pythran.dist.PythranExtension(
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/pythran/dist.py", line 131, in __init__
cfg_ext = cfg.make_extension(python=True, **kwargs)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/pythran/config.py", line 220, in make_extension
numpy_blas = numpy_sys.get_info(user_blas)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 584, in get_info
return cl().get_info(notfound_action)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 844, in get_info
self.calc_info()
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 2040, in calc_info
info = self.check_libs(lib_dirs, blas_libs, [])
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 986, in check_libs
info = self._check_libs(lib_dirs, libs, opt_libs, [ext])
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 1057, in _check_libs
found_dirs, found_libs = self._find_libs(lib_dirs, libs, exts)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 1041, in _find_libs
found_lib = self._find_lib(lib_dir, lib, exts)
File "/Users/runner/hostedtoolcache/Python/3.9.1/x64/lib/python3.9/site-packages/numpy/distutils/system_info.py", line 1022, in _find_lib
raise RuntimeError(_accel_msg.format(filename=p[0]))
RuntimeError: Found /usr/lib/libblas.dylib, but that file is a symbolic link to the MacOS Accelerate framework, which is not supported by NumPy. You must configure the build to use a different optimized library, or disable the use of optimized BLAS and LAPACK by setting the environment variables NPY_BLAS_ORDER="" and NPY_LAPACK_ORDER="" before building NumPy.

Build failed! (0:01:47.617718 elapsed)
Error: Process completed with exit code 1.

Issue 2:
My issue is about how to use make_lsq_spline() method correctly. I am using spicy 1.3 and numpy 1.16.3.

Reproducing code example:

import numpy as np
import scipy.interpolate as si

x = np.array([0.03350967, 0.06701934, 0.100529 , 0.13403867, 0.16754834,
0.20105801, 0.23456768, 0.26807734, 0.30158701, 0.33509668,
0.36860635, 0.40211602, 0.43562568, 0.46913535, 0.50264502,
0.53615469, 0.56966435, 0.60317402, 0.63668369, 0.67019336,
0.70370303, 0.73721269, 0.77072236, 0.80423203, 0.8377417 ,
0.87125137, 0.90476103, 0.9382707 , 0.97178037, 1.00529004,
1.03879971, 1.07230937, 1.10581904, 1.13932871, 1.17283838,
1.20634805, 1.23985771, 1.27336738, 1.30687705, 1.34038672,
1.37389639, 1.40740605, 1.44091572, 1.47442539, 1.50793506,
1.54144472, 1.57495439, 1.60846406, 1.64197373, 1.6754834 ,
1.70899306, 1.74250273, 1.7760124 , 1.80952207, 1.84303174])

y = np.array([0.1040807 , 0.10382307, 0.10323297, 0.10276147, 0.10257906,
0.10253339, 0.10236513, 0.10225094, 0.10208078, 0.10168483,
0.10103374, 0.10016549, 0.0992114 , 0.09833254, 0.09753467,
0.09679354, 0.09588709, 0.09510592, 0.09425722, 0.09309047,
0.09207683, 0.09155676, 0.09093702, 0.09022714, 0.08975676,
0.08955236, 0.08930825, 0.11663662, 0.11668795, 0.11723575,
0.11800538, 0.11901272, 0.12012716, 0.12158163, 0.12319893,
0.12419895, 0.12573243, 0.1254061 , 0.1250039 , 0.12455747,
0.124469 , 0.1247247 , 0.12429177, 0.12363416, 0.12318804,
0.12259555, 0.12239772, 0.12225429, 0.12194444, 0.12136568,
0.12067843, 0.11981264, 0.11873786, 0.11807431, 0.11748397])

knots=np.linspace(x[0],x[-1],5)
t=np.r_[(x[0],)*4, knots, (x[-1],)*4]
spl=si.make_lsq_spline(x,y,t)

Error message:

---------------------------------------------------------------------------
LinAlgError Traceback (most recent call last)
<ipython-input-33-c19ae7c64e41> in <module>
----> 1 spl2=si.make_lsq_spline(x,y,t)

/usr/local/lib/python3.7/site-packages/scipy/interpolate/_bsplines.py in make_lsq_spline(x, y, t, k, w, axis, check_finite)
1015 # have observation matrix & rhs, can solve the LSQ problem
1016 cho_decomp = cholesky_banded(ab, overwrite_ab=True, lower=lower,
-> 1017 check_finite=check_finite)
1018 c = cho_solve_banded((cho_decomp, lower), rhs, overwrite_b=True,
1019 check_finite=check_finite)

/usr/local/lib/python3.7/site-packages/scipy/linalg/decomp_cholesky.py in cholesky_banded(ab, overwrite_ab, lower, check_finite)
280 c, info = pbtrf(ab, lower=lower, overwrite_ab=overwrite_ab)
281 if info > 0:
--> 282 raise LinAlgError("%d-th leading minor not positive definite" % info)
283 if info < 0:
284 raise ValueError('illegal value in %d-th argument of internal pbtrf'

LinAlgError: 1-th leading minor not positive definite

Scipy/Numpy/Python version information:

import sys, scipy, numpy; print(scipy.__version__, numpy.__version__, sys.version_info)
1.3.0 1.16.3 sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)