pip_parse regression in 0.3.0

[caseyduquettesc]

🐞 bug report

Affected Rule

The issue is caused by the rule: pip_parse

Is this a regression?

Yes, the previous version in which this bug was not present was: 0.2.0

Description

Depending on google-api-core fails when using pip_parse from 0.3.0, but succeeds in 0.2.0.
pip_install works in both versions.

Originally reported in #431, but was triaged as a new issue here - #431 (comment)

🔬 Minimal Reproduction

https://github.com/caseyduquettesc/rules_python_demo

% bazel run //scripts/demo
INFO: Invocation ID: 3dd0bf13-d654-44ff-b250-34e69abb2cd7
INFO: Analyzed target //scripts/demo:demo (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //scripts/demo:demo up-to-date:
  bazel-bin/scripts/demo/demo
INFO: Elapsed time: 0.217s, Critical Path: 0.02s
INFO: 1 process: 1 internal.
INFO: Running command line: bazel-bin/scripts/demo/demo
INFO: Build Event Protocol files produced successfully.
INFO: Build completed successfully, 1 total action
Traceback (most recent call last):
  File "/Users/.cache/_bazel_root/3e48c9752578ebae810f99b25573480c/execroot/demo/bazel-out/darwin-fastbuild/bin/scripts/demo/demo.runfiles/demo/scripts/demo/demo.py", line 1, in <module>
    from google.api_core.exceptions import ResourceExhausted
ModuleNotFoundError: No module named 'google.api_core'

🔥 Exception or Error

Traceback (most recent call last):
  File "/Users/.cache/_bazel_root/3e48c9752578ebae810f99b25573480c/execroot/demo/bazel-out/darwin-fastbuild/bin/scripts/demo/demo.runfiles/demo/scripts/demo/demo.py", line 1, in 
    from google.api_core.exceptions import ResourceExhausted
ModuleNotFoundError: No module named 'google.api_core'

🌍 Your Environment

Operating System:

MacOS 10.15.7

Output of bazel version:

Build label: 4.1.0.188
Build target: bazel-out/darwin-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Mon Jun 21 23:14:47 2021 (1624317287)
Build timestamp: 1624317287
Build timestamp as int: 1624317287

Rules_python version:

0.3.0

Anything else relevant?
Originally posted in #431 (comment)