# cat /etc/issue
Ubuntu 20.04.3 LTS \n \l

# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.3 LTS
Release:        20.04
Codename:       focal
# uname -a
Linux 1e2b03352168 5.10.16.3-microsoft-standard-WSL2 #1 SMP Fri Apr 2 22:23:49 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

# python3 --version
Python 3.8.10
# pip3 --version
pip 21.3.1 from /usr/local/lib/python3.8/dist-packages/pip (python 3.8)

# echo pip-tools > req.in
# cat req.in
pip-tools
# pip-compile req.in
#
# This file is autogenerated by pip-compile with python 3.8
# To update, run:
#
#    pip-compile req.in
#
click==8.0.3
    # via pip-tools
pep517==0.12.0
    # via pip-tools
pip-tools==6.4.0
    # via -r req.in
tomli==2.0.0
    # via pep517
wheel==0.37.1
    # via pip-tools

# The following packages are considered to be unsafe in a requirements file:
# pip
# setuptools

# echo nbviewer > req.in
# cat req.in
nbviewer
# pip-compile req.in
    ERROR: Command errored out with exit status 1:
     command: /usr/bin/python3 -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-resolver-njyh27nz/futures/setup.py'"'"'; __file__='"'"'/tmp/pip-resolver-njyh27nz/futures/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-snm5v3mu
         cwd: /tmp/pip-resolver-njyh27nz/futures/
    Complete output (24 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/usr/local/lib/python3.8/dist-packages/setuptools/__init__.py", line 18, in <module>
        from setuptools.dist import Distribution
      File "/usr/local/lib/python3.8/dist-packages/setuptools/dist.py", line 31, in <module>
        from setuptools.extern.more_itertools import unique_everseen
      File "<frozen importlib._bootstrap>", line 991, in _find_and_load
      File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 657, in _load_unlocked
      File "<frozen importlib._bootstrap>", line 556, in module_from_spec
      File "/usr/local/lib/python3.8/dist-packages/setuptools/extern/__init__.py", line 52, in create_module
        return self.load_module(spec.name)
      File "/usr/local/lib/python3.8/dist-packages/setuptools/extern/__init__.py", line 37, in load_module
        __import__(extant)
      File "/usr/local/lib/python3.8/dist-packages/setuptools/_vendor/more_itertools/__init__.py", line 1, in <module>
        from .more import *  # noqa
      File "/usr/local/lib/python3.8/dist-packages/setuptools/_vendor/more_itertools/more.py", line 5, in <module>
        from concurrent.futures import ThreadPoolExecutor
      File "/tmp/pip-resolver-njyh27nz/futures/concurrent/futures/__init__.py", line 8, in <module>
        from concurrent.futures._base import (FIRST_COMPLETED,
      File "/tmp/pip-resolver-njyh27nz/futures/concurrent/futures/_base.py", line 357
        raise type(self._exception), self._exception, self._traceback
                                   ^
    SyntaxError: invalid syntax
    ----------------------------------------
Traceback (most recent call last):
  File "/usr/local/bin/pip-compile", line 8, in <module>
    sys.exit(cli())
  File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/piptools/scripts/compile.py", line 466, in cli
    results = resolver.resolve(max_rounds=max_rounds)
  File "/usr/local/lib/python3.8/dist-packages/piptools/resolver.py", line 175, in resolve
    has_changed, best_matches = self._resolve_one_round()
  File "/usr/local/lib/python3.8/dist-packages/piptools/resolver.py", line 319, in _resolve_one_round
    their_constraints.extend(self._iter_dependencies(best_match))
  File "/usr/local/lib/python3.8/dist-packages/piptools/resolver.py", line 428, in _iter_dependencies
    dependencies = self.repository.get_dependencies(ireq)
  File "/usr/local/lib/python3.8/dist-packages/piptools/repositories/local.py", line 79, in get_dependencies
    return self.repository.get_dependencies(ireq)
  File "/usr/local/lib/python3.8/dist-packages/piptools/repositories/pypi.py", line 236, in get_dependencies
    self._dependencies_cache[ireq] = self.resolve_reqs(
  File "/usr/local/lib/python3.8/dist-packages/piptools/repositories/pypi.py", line 199, in resolve_reqs
    results = resolver._resolve_one(reqset, ireq)
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/resolution/legacy/resolver.py", line 379, in _resolve_one
    dist = self._get_dist_for(req_to_install)
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/resolution/legacy/resolver.py", line 332, in _get_dist_for
    dist = self.preparer.prepare_linked_requirement(req)
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/operations/prepare.py", line 482, in prepare_linked_requirement
    return self._prepare_linked_requirement(req, parallel_builds)
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/operations/prepare.py", line 546, in _prepare_linked_requirement
    dist = _get_prepared_distribution(
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/operations/prepare.py", line 58, in _get_prepared_distribution
    abstract_dist.prepare_distribution_metadata(finder, build_isolation)
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/distributions/sdist.py", line 49, in prepare_distribution_metadata
    self.req.prepare_metadata()
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/req/req_install.py", line 561, in prepare_metadata
    self.metadata_directory = generate_metadata_legacy(
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/operations/build/metadata_legacy.py", line 59, in generate_metadata
    call_subprocess(
  File "/usr/local/lib/python3.8/dist-packages/pip/_internal/utils/subprocess.py", line 254, in call_subprocess
    raise InstallationSubprocessError(proc.returncode, command_desc)
pip._internal.exceptions.InstallationSubprocessError: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.