catch TypeError if magma is not available

[Eloitor]

When magma is not available it raises a TypeError.

sage: BruhatTitsQuotient(2, 3)
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
...

TypeError: unable to start magma because the command 'magma -n' failed: The command was not found or was not executable: magma.

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⌛ Dependencies

[github-actions]

Documentation preview for this PR (built with commit 9750c2e; changes) is ready! 🎉
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[user202729]

surely it should be raising RuntimeError instead? Maybe fix the downstream to raise RuntimeError? (… and current upstream codes?)

[Eloitor]

do you mean here? https://github.com/sagemath/sage/blob/9352a3258c04bd5528f9df11e86e288a1c94884f/src/sage/interfaces/expect.py#L1520C1-L1524C41

[user202729]

Hm, that sounds like large refactor effort. Feel easiest to make a special PexpectError that (for now) inherit from TypeError, but can be changed in the future.