Issue 1:
Installing versions > 1.3.13 is failing for us, it appears due to an integrated enum dependency.

When using 1.3.13 this was not an issue. Builds with 1.3.14 and 1.3.15 fail in this way.

Error:

AttributeError: module 'enum' has no attribute 'IntFlag'

Stack:

Python 3.7.4

pipenv for dependency management

sqlalchemy = "*" dependency line

Output during pipenv install:

An error occurred while installing sqlalchemy==1.3.14 --hash=sha256:b92d2de62e43499d85b1780274d1b562e5159c7996f6f04a9bb46cf681ced45f! Will try again.
Installing initially failed dependencies…
[pipenv.exceptions.InstallError]: File "/usr/local/lib/python3.7/site-packages/pipenv/core.py", line 1874, in do_install
[pipenv.exceptions.InstallError]: keep_outdated=keep_outdated
[pipenv.exceptions.InstallError]: File "/usr/local/lib/python3.7/site-packages/pipenv/core.py", line 1253, in do_init
[pipenv.exceptions.InstallError]: pypi_mirror=pypi_mirror,
[pipenv.exceptions.InstallError]: File "/usr/local/lib/python3.7/site-packages/pipenv/core.py", line 859, in do_install_dependencies
[pipenv.exceptions.InstallError]: retry_list, procs, failed_deps_queue, requirements_dir, **install_kwargs
[pipenv.exceptions.InstallError]: File "/usr/local/lib/python3.7/site-packages/pipenv/core.py", line 763, in batch_install
[pipenv.exceptions.InstallError]: _cleanup_procs(procs, not blocking, failed_deps_queue, retry=retry)
[pipenv.exceptions.InstallError]: File "/usr/local/lib/python3.7/site-packages/pipenv/core.py", line 681, in _cleanup_procs
[pipenv.exceptions.InstallError]: raise exceptions.InstallError(c.dep.name, extra=err_lines)
[pipenv.exceptions.InstallError]: ['Collecting sqlalchemy==1.3.14', ' Using cached SQLAlchemy-1.3.14.tar.gz (6.1 MB)', ' Installing build dependencies: started', " Installing build dependencies: finished with status 'error'"]
[pipenv.exceptions.InstallError]: ['ERROR: Command errored out with exit status 1:', " command: /root/.local/share/virtualenvs/ks-nQj0AsbL/bin/python /root/.local/share/virtualenvs/ks-nQj0AsbL/lib/python3.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-daar_xok/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel", ' cwd: None', ' Complete output (14 lines):', ' Traceback (most recent call last):', ' File "/usr/local/lib/python3.7/runpy.py", line 193, in _run_module_as_main', ' "__main__", mod_spec)', ' File "/usr/local/lib/python3.7/runpy.py", line 85, in _run_code', ' exec(code, run_globals)', ' File "/root/.local/share/virtualenvs/ks-nQj0AsbL/lib/python3.7/site-packages/pip/__main__.py", line 16, in <module>', ' from pip._internal.cli.main import main as _main # isort:skip # noqa', ' File "/root/.local/share/virtualenvs/ks-nQj0AsbL/lib/python3.7/site-packages/pip/_internal/cli/main.py", line 5, in <module>', ' import locale', ' File "/usr/local/lib/python3.7/locale.py", line 16, in <module>', ' import re', ' File "/usr/local/lib/python3.7/re.py", line 143, in <module>', ' class RegexFlag(enum.IntFlag):', " AttributeError: module 'enum' has no attribute 'IntFlag'", ' ----------------------------------------', "ERROR: Command errored out with exit status 1: /root/.local/share/virtualenvs/ks-nQj0AsbL/bin/python /root/.local/share/virtualenvs/ks-nQj0AsbL/lib/python3.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-daar_xok/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel Check the logs for full command output."]

Issue 2:
python 3.7

sqlalchemy 1.3.14

'ERROR: Command errored out with exit status 1:',
" command: /root/projects/py/custom-api/.venv/bin/python /root/projects/py/custom-api/.venv/lib/python3.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-8yd681ix/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel",
' cwd: None',
' Complete output (14 lines):',
' Traceback (most recent call last):',
' File "/usr/lib/python3.7/runpy.py", line 193, in _run_module_as_main',
' "__main__", mod_spec)',
' File "/usr/lib/python3.7/runpy.py", line 85, in _run_code',
' exec(code, run_globals)',
' File "/root/projects/py/custom-api/.venv/lib/python3.7/site-packages/pip/__main__.py", line 16, in <module>',
' from pip._internal.cli.main import main as _main # isort:skip # noqa',
' File "/root/projects/py/custom-api/.venv/lib/python3.7/site-packages/pip/_internal/cli/main.py", line 5, in <module>',
' import locale',
' File "/usr/lib/python3.7/locale.py", line 16, in <module>',
' import re',
' File "/usr/lib/python3.7/re.py", line 143, in <module>',
' class RegexFlag(enum.IntFlag):',
" AttributeError: module 'enum' has no attribute 'IntFlag'",
' ----------------------------------------',
"ERROR: Command errored out with exit status 1: /root/projects/py/custom-api/.venv/bin/python /root/projects/py/custom-api/.venv/lib/python3.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-8yd681ix/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel Check the logs for full command output."