AttributeError: 'NoneType' object has no attribute 'is_hash_allowed'

Environment

• pip version: 19.2
• Python version: 3.6.8
• OS: Mac OSX (Darwin Kernel Version 18.6.0)

Description I made env update in my project including pip as well. After that I wanted to check outdated packages with command:

pip list --outdated --format=columns

After that exception was raised.

Expected behavior I expected list of packages or empty list.

How to Reproduce

1. Get the newest version of package from PyPI.
2. Then run pip list --outdated --format=columns
3. An error occurs.

Output

(env) project (develop) $ pip list --outdated --format=columns
ERROR: Exception:
Traceback (most recent call last):
  File "/project/env/lib/python3.6/site-packages/pip/_internal/cli/base_command.py", line 188, in main
    status = self.run(options, args)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/commands/list.py", line 156, in run
    packages = self.get_outdated(packages, options)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/commands/list.py", line 164, in get_outdated
    dist for dist in self.iter_packages_latest_infos(packages, options)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/commands/list.py", line 164, in <listcomp>
    dist for dist in self.iter_packages_latest_infos(packages, options)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/commands/list.py", line 195, in iter_packages_latest_infos
    best_candidate = evaluator.get_best_candidate(all_candidates)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/index.py", line 729, in get_best_candidate
    best_candidate = max(candidates, key=self._sort_key)
  File "/project/env/lib/python3.6/site-packages/pip/_internal/index.py", line 710, in _sort_key
    has_allowed_hash = int(link.is_hash_allowed(self._hashes))
  File "/project/env/lib/python3.6/site-packages/pip/_internal/models/link.py", line 213, in is_hash_allowed
    return hashes.is_hash_allowed(self.hash_name, hex_digest=self.hash)
AttributeError: 'NoneType' object has no attribute 'is_hash_allowed'

[pradyunsg]

The fix is in master. I’ll do the release in a bit – getting a bit of rest after a long day today.

[pradyunsg]

The release with this bug-fix has been uploaded. Thanks everyone (and especially @cjerdonek)! 😃