fix(lib-injection): ensure sitecustomize.py supports Python 2.7+ [backport 2.17]

[github-actions[bot]]

Backport 739a8c7742b778117605935617cdaf80cc662cdd from #11381 to 2.17.

We must insure that the lib-injection works properly with older versions of Python. Even ones that we don't support with our library. This is because SSI will inject into any python process.

The oldest conceivable version in the wild is likely 2.6, although since it relies on OpenSSL 1.0, I hope most people have at least moved on to 2.7.

The current implementation of the loader had syntax errors that would raise when trying to execute the script. With sitecustomize.py we will not crash the application due to an error because Python try/excepts it, but it does mean the script won't load / we won't get telemetry data.

Majority of the changes are to remove f-strings and type hinting. I added a few extra guards and an additional telemetry generation around the main try: _inject() except: block.

Checklist

• [x] PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• [x] Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[pr-commenter[bot]]

Benchmarks

Benchmark execution time: 2024-11-18 21:09:53

Comparing candidate commit 880ddb37791bd4a055777e2f06f1c948419a7365 in PR branch backport-11381-to-2.17 with baseline commit 7ec870177320cb2a6fcb40196ad91373d18ce3fe in branch 2.17.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 388 metrics, 2 unstable metrics.

[github-actions[bot]]

CODEOWNERS have been resolved as:

.github/workflows/test_lib_injection.yml                                @DataDog/python-guild @DataDog/apm-core-python
releasenotes/notes/fix-lib-injection-version-support-ae2ff3a79ac1f6f2.yaml  @DataDog/apm-python
lib-injection/sources/sitecustomize.py                                  @DataDog/apm-core-python