Python 3.13/3.14 compatibility: fix escape sequence and cgi removal

[marcelo-srs]

Summary

This PR fixes three Python 3.13/3.14 compatibility issues found when using remi with PyInstaller and modern Python versions.

1. Fix invalid escape sequence \E in server.py (SyntaxWarning → SyntaxError)

remi/server.py contained \ERROR in a debug format string. \E is not a valid Python escape sequence:

• Python 3.12: emits SyntaxWarning
• Python 3.13: emits SyntaxWarning (promoted to error by PyInstaller in frozen builds)
• Python 3.14: hard SyntaxError — the module fails to import entirely

Fix: changed \ERROR → \\ERROR.

2. Replace removed cgi module

cgi.FieldStorage was deprecated in Python 3.11 and removed in Python 3.13. It was used in do_POST to parse multipart/form-data file uploads.

Fix: wrapped the import in a try/except:

• Python ≤ 3.12: imports cgi.FieldStorage as before — no behaviour change
• Python 3.13+: uses a minimal _FieldStorage drop-in built on email.parser that exposes the same .keys() / .__getitem__() / .filename / .file interface

3. Ensure remi.__version__ is always defined (PyInstaller / frozen builds)

__init__.py looked up the version via importlib.metadata, then pkg_resources, and silently passed if neither could find the package. In PyInstaller frozen builds the package metadata is typically absent, leaving __version__ undefined and causing AttributeError on access.

Fix: set __version__ = _FALLBACK_VERSION (hardcoded "2026.03.24") before the lookup chain. The metadata lookup still overrides it when available; the fallback guarantees __version__ is always a valid string.

Version bumped to 2026.03.24 in both __init__.py and setup.py.

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New tests — test/test_version.py

Test	What it covers
TestNoSyntaxWarnings.test_server_py_no_syntax_warnings	Compiles server.py with -W error::SyntaxWarning — asserts no warnings/errors
TestVersionAlwaysDefined.test_version_is_string	remi.__version__ is always a str
TestVersionAlwaysDefined.test_version_non_empty	remi.__version__ is never empty
TestVersionImportlibMetadataPath.test_importlib_metadata_used	When importlib.metadata.version() succeeds, its value is used
TestVersionPkgResourcesFallback.test_pkg_resources_fallback	When importlib.metadata is absent, pkg_resources provides the version
TestVersionHardcodedFallback.test_hardcoded_fallback_used	When metadata lookup raises PackageNotFoundError, hardcoded fallback is used
TestVersionHardcodedFallback.test_fallback_version_matches_setup	_FALLBACK_VERSION in __init__.py stays in sync with setup.py

---

Test results across Python versions

All 7 new tests pass on every tested version. The 4 pre-existing failures (missing optional matplotlib/PIL deps, and two assertEquals calls deprecated since 3.12) are unchanged and unrelated to this PR.

Python 3.12.8

Ran 95 tests in 2.146s
FAILED (errors=4 [pre-existing], skipped=8)
New version tests: 7/7 ✅
SyntaxWarning check: ✅

Python 3.13.1

Ran 95 tests in 2.130s
FAILED (errors=4 [pre-existing], skipped=8)
New version tests: 7/7 ✅
SyntaxWarning check: ✅

Python 3.14.3

Ran 95 tests in 2.143s
FAILED (errors=4 [pre-existing], skipped=8)
New version tests: 7/7 ✅
SyntaxWarning check: ✅

Note for PyInstaller users: the pkg_resources injection workaround previously needed in launcher scripts is no longer required — importlib.metadata takes priority on Python 3.8+ and the hardcoded fallback covers frozen-build environments.

🤖 Generated with Claude Code

[dddomodossola]

Thank you very much @marcelo-srs 😉