Make feature TeXFile check latex first

[soehms]

Currently, as observed in comment 7 of #34185, the method is_present of instances of class TeXFile runs into an exception if latex is not installed. For example:

sage: from sage.features.latex import LaTeXPackage
sage: LaTeXPackage("tkz-graph").is_present()
Traceback (most recent call last):
...
FileNotFoundError: [Errno 2] No such file or directory: 'kpsewhich'

The aim of the ticket is to fix this.

CC: @seblabbe

Component: doctest framework

Keywords: latex texfile feature

Author: Sebastian Oehms, Kwankyu Lee

Branch/Commit: a77ff0c

Reviewer: Kwankyu Lee, Sebastian Oehms

Issue created by migration from https://trac.sagemath.org/ticket/34282

[soehms]

Branch: u/soehms/join_feature_texfile_with_pdflatex_34282

[soehms]

Commit: c599e49

[soehms]

New commits:

c599e49

34282: initial

[soehms]

Author: Sebastian Oehms

[mkoeppe]

comment:3

I think it would also make sense to add spkg='texlive' to these features

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

7358dc2

34282: dd spkg='texlive', refactoring, pycodestyle

[sagetrac-git]

Changed commit from c599e49 to 7358dc2

[soehms]

comment:5

Replying to @mkoeppe:

I think it would also make sense to add spkg='texlive' to these features

Done! Furthermore, I refactor the executable features not only to avoid duplicated code, but also since in my point of view it is not reasonable that just the latex feature has a stronger is_functional check.