fix(iast): None as module_path at astpatch_module

[gnufede]

IAST: Fixes an issue where the AST patching process fails when the origin of a module is reported as None, raising a FileNotFoundError as follows:

Traceback (most recent call last):
  File "/Users/federico.mon/go/src/github.com/DataDog/dd-trace-py/ddtrace/appsec/_iast/_ast/ast_patching.py", line 130, in astpatch_module
    if os.stat(module_path).st_size == 0:
FileNotFoundError: [Errno 2] No such file or directory: 'None'

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Description motivates each change
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Change is maintainable (easy to change, telemetry, documentation)
• Release note makes sense to a user of the library
• 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

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: gnufede/APPSEC-52604-fix-none-module_path
Commit report: 80d1507
Test service: dd-trace-py

✅ 0 Failed, 615 Passed, 110988 Skipped, 17m 10.25s Total duration (1h 33m 54.89s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-04-15 09:39:02

Comparing candidate commit 40b3f2d in PR branch gnufede/APPSEC-52604-fix-none-module_path with baseline commit d7c368f in branch main.

Found 8 performance improvements and 1 performance regressions! Performance is the same for 192 metrics, 9 unstable metrics.

scenario:flasksimple-appsec-get

• 🟩 execution_time [-243.641µs; -190.455µs] or [-3.746%; -2.928%]

scenario:httppropagationextract-datadog_tracecontext_tracestate_not_propagated_on_trace_id_no_match

• 🟥 max_rss_usage [+695.502KB; +771.685KB] or [+3.287%; +3.646%]

scenario:httppropagationinject-ids_only

• 🟩 max_rss_usage [-763.805KB; -700.105KB] or [-3.493%; -3.202%]

scenario:httppropagationinject-with_dd_origin

• 🟩 max_rss_usage [-1.092MB; -1.035MB] or [-4.994%; -4.734%]

scenario:httppropagationinject-with_sampling_priority

• 🟩 max_rss_usage [-773.732KB; -717.212KB] or [-3.538%; -3.280%]

scenario:httppropagationinject-with_tags

• 🟩 max_rss_usage [-640.440KB; -585.903KB] or [-2.929%; -2.680%]

scenario:httppropagationinject-with_tags_invalid

• 🟩 max_rss_usage [-632.202KB; -579.804KB] or [-2.893%; -2.653%]

scenario:httppropagationinject-with_tags_max_size

• 🟩 max_rss_usage [-631.183KB; -574.269KB] or [-2.887%; -2.626%]

scenario:span-start-finish

• 🟩 max_rss_usage [-738.405KB; -483.022KB] or [-3.380%; -2.211%]