Add code comment re: base64-encoded code in virtualenv.py

[cjerdonek]

I think it would help to add a code comment near here explaining why virtualenv.py includes base-64 encoded Python scripts, and where the sources for the scripts come from (e.g. are the human-readable versions stored or copied from elsewhere or are these the sources).

I came across this issue while troubleshooting issue #281. The decoded version of DISTRIBUTE_SETUP_PY was being passed as the command-line argument to a subprocess call that wasn't behaving as expected. The script being base-64 encoded makes the issue harder to debug and troubleshoot (and in particular, modify).

[cjerdonek]

I see now that the original sources are in the directory named virtualenv_embedded, though this can be mentioned.

[cjerdonek]

I think the code comment should also include instructions on how to update the base-64 encoded strings in virtualenv.py from the source files located in the virtualenv_embedded directory. In particular, does the source tree have a helper script to do this for you automatically, or is this a manual step?

[stale]

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[cjerdonek]

Keep open.

[gaborbernat]

We indeed should document this, one should use the embed tox target (we now break the CI if someone forgets to do this).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Just add a comment if you want to keep it open. Thank you for your contributions.

[gaborbernat]

This is becoming obsolete with #1366 now in full swing.