Fix bare except clause in setup.py

[koteshyelamati]

Replace bare except: with except ImportError: in setup.py.

The guarded block imports from setuptools — specifically from setuptools import .... The only exception that can reasonably be raised here is ImportError (when setuptools is not installed). Using except ImportError: makes the intent explicit and avoids accidentally swallowing KeyboardInterrupt or SystemExit.

[polybassa]

Thanks for the PR, please fix the commit validity check.

[koteshyelamati]

Thank you for the review, @polybassa! Could you clarify what the commit validity check requires? I see the "Check the validity of the commits" CI check is failing — is this a DCO sign-off (Signed-off-by) requirement, or a commit message format issue? I'll be happy to fix it once I know what's needed.

[polybassa]

ERROR: Commit 00fd2e3ba5a9e3649e4116969a6838c3d1de10b5 is missing the 'AI-Assisted: yes|no [tool(s)]' trailer.

[itzzdev09]

Confirmed correct, and I dug into why this one survived — which seems worth recording, since the fix alone doesn't stop it recurring.

E722 is not in the project's ignore list (ignore = E203, E731, W504, W503), so flake8 does flag bare excepts. Running it directly on the file:

$ flake8 setup.py
setup.py:19:1: E722 do not use bare 'except'
setup.py:97:89: E501 line too long (93 > 88 characters)

The reason CI never saw it is the lint target:

[testenv:flake8]
commands = flake8 scapy/

setup.py sits at the repo root, outside scapy/, so it's never linted. That also explains why this is the only bare except: left in the tree — grep finds exactly one occurrence repo-wide, and it happens to be in the one Python file the linter doesn't cover.

After the change in this PR, flake8 setup.py reports only the pre-existing E501 on line 97.

On correctness: from setuptools import ... raises ImportError when setuptools is missing (ModuleNotFoundError subclasses it, so that's covered too), and the narrowing does the intended job of no longer converting a KeyboardInterrupt during import into "setuptools is required to install scapy !".

Two things maintainers might want to decide alongside this:

1. Whether to widen the lint target to catch regressions — something like flake8 scapy/ setup.py. That would also surface the E501 on line 97, so it isn't a zero-diff change.
2. Whether the raise ImportError(...) should be raise ImportError(...) from None. As written the original traceback is chained in as __context__, so the user sees both the underlying import failure and the friendly message. That's arguably useful here, so it may be intentional — just noting it since the PR is already touching this handler.

Neither blocks the change; the PR is a strict improvement as-is.

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Disclosure: reviewed with AI assistance (Claude Code). The flake8 output above is from actually running it against this file, before and after the change.