# Buggy code
def box(self, instance, instance_type, val):
    if isinstance(val, string_types):
        val = val.replace(" ", ",").split(",")
    return super(_FeaturesField, self).box(instance, instance_type, val)


# Traceback (RuntimeError)
(base) [nwani@centos7-nwani scratch]$ conda install scratch -c local
Solving environment: failed

# >>>>>>>>>>>>>>>>>>>>>> ERROR REPORT <<<<<<<<<<<<<<<<<<<<<<

Traceback (most recent call last):
File "/home/nwani/m2/lib/python2.7/site-packages/conda/exceptions.py", line 789, in __call__
return func(*args, **kwargs)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/cli/main.py", line 78, in _main
exit_code = do_call(args, p)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/cli/conda_argparse.py", line 77, in do_call
exit_code = getattr(module, func_name)(args, parser)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/cli/main_install.py", line 11, in execute
install(args, parser, 'install')
File "/home/nwani/m2/lib/python2.7/site-packages/conda/cli/install.py", line 236, in install
force_reinstall=context.force,
File "/home/nwani/m2/lib/python2.7/site-packages/conda/core/solve.py", line 504, in solve_for_transaction
force_remove, force_reinstall)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/core/solve.py", line 437, in solve_for_diff
final_precs = self.solve_final_state(deps_modifier, prune, ignore_pinned, force_remove)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/core/solve.py", line 317, in solve_final_state
conflicting_specs = r.get_conflicting_specs(tuple(final_environment_specs))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 705, in get_conflicting_specs
C = r2.gen_clauses()
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 505, in gen_clauses
C.Require(C.Or, nkey, self.push_MatchSpec(C, ms))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 477, in push_MatchSpec
m = C.from_name(self.push_MatchSpec(C, ms2))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 477, in push_MatchSpec
m = C.from_name(self.push_MatchSpec(C, ms2))
...yada...
...yada...
...yada...
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 477, in push_MatchSpec
m = C.from_name(self.push_MatchSpec(C, ms2))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 477, in push_MatchSpec
m = C.from_name(self.push_MatchSpec(C, ms2))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 477, in push_MatchSpec
m = C.from_name(self.push_MatchSpec(C, ms2))
File "/home/nwani/m2/lib/python2.7/site-packages/conda/resolve.py", line 476, in push_MatchSpec
ms2 = MatchSpec(track_features=tf) if tf else MatchSpec(nm)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/models/match_spec.py", line 76, in __call__
return super(MatchSpecType, cls).__call__(**kwargs)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/models/match_spec.py", line 178, in __init__
self._match_components = self._build_components(**kwargs)
File "/home/nwani/m2/lib/python2.7/site-packages/conda/models/match_spec.py", line 365, in _build_components
return frozendict(_make(key, value) for key, value in iteritems(kwargs))
File "/home/nwani/m2/lib/python2.7/collections.py", line 69, in __init__
self.__update(*args, **kwds)
File "/home/nwani/m2/lib/python2.7/_abcoll.py", line 564, in update
if isinstance(other, Mapping):
File "/home/nwani/m2/lib/python2.7/abc.py", line 141, in __instancecheck__
subtype in cls._abc_negative_cache):
File "/home/nwani/m2/lib/python2.7/_weakrefset.py", line 75, in __contains__
return wr in self.data
RuntimeError: maximum recursion depth exceeded in cmp

`$ /home/nwani/m2/bin/conda install scratch -c local`

environment variables:
CIO_TEST=<not set>
CONDA_DEFAULT_ENV=base
CONDA_PREFIX=/home/nwani/m2
CONDA_PROMPT_MODIFIER=(base)
CONDA_PYTHON_EXE=/home/nwani/m2/bin/python
CONDA_ROOT=/home/nwani/m2
CONDA_SHLVL=1
PATH=/home/nwani/m2/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/
home/nwani/.local/bin:/home/nwani/bin
REQUESTS_CA_BUNDLE=<not set>
SSL_CERT_FILE=<not set>

active environment : base
active env location : /home/nwani/m2
shell level : 1
user config file : /home/nwani/.condarc
populated config files :
conda version : 4.4.9
conda-build version : 3.4.1
python version : 2.7.14.final.0
base environment : /home/nwani/m2  (writable)
channel URLs : file:///home/nwani/m2/conda-bld/linux-64
file:///home/nwani/m2/conda-bld/noarch
https://repo.continuum.io/pkgs/main/linux-64
https://repo.continuum.io/pkgs/main/noarch
https://repo.continuum.io/pkgs/free/linux-64
https://repo.continuum.io/pkgs/free/noarch
https://repo.continuum.io/pkgs/r/linux-64
https://repo.continuum.io/pkgs/r/noarch
https://repo.continuum.io/pkgs/pro/linux-64
https://repo.continuum.io/pkgs/pro/noarch
package cache : /home/nwani/m2/pkgs
/home/nwani/.conda/pkgs
envs directories : /home/nwani/m2/envs
/home/nwani/.conda/envs
platform : linux-64
user-agent : conda/4.4.9 requests/2.18.4 CPython/2.7.14 Linux/3.10.0-693.5.2.el7.x86_64 centos/7 glibc/2.17
UID:GID : 1001:1001
netrc file : None
offline mode : False


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# Fixed code
def box(self, instance, instance_type, val):
    if isinstance(val, string_types):
        val = val.replace(" ", ",").split(",")
    val = tuple(f for f in (ff.strip() for ff in val) if f)
    return super(_FeaturesField, self).box(instance, instance_type, val)