retry fetching source file for extensions from PyPI with alternative filename (with - replaced with _ in extension name)

[smoors]

if downloading an extension fails, retry by replacing hyphen with underscore in the name: abc-def-%(version).tar.gz -> abc_def-%(version).tar.gz

only done if:

• it's an extension
• download from PyPI
• there's only 1 source url
• default filename is used (no sources or source_tmpl specified)

when this is merged, i would recommend to always use the exact name of the package listed on PyPI as the extension name:

• it ensures EB tries to download the 2 name formats if there are hyphens in the name
• users are more likely to search for this name when using e.g. module spider <package>
• it standardizes the naming of extensions in Lmod (module spider), avoiding that the same package is available with 2 different names, and thus easier to find all installed versions.

at some point we might consider switching to the underscore for the tarball on the first try, as that is the recommended name format, see
https://packaging.python.org/en/latest/specifications/source-distribution-format/#source-distribution-file-name

[Flamefire]

at some point we should probably switch to using the underscore in the first try,

Couldn't there be packages like very_cool-software? And some packages are named foo_bar or on PyPI so we should keep the spelling of PyPI although in general it should by hyphens.

[smoors]

at some point we should probably switch to using the underscore in the first try,

Couldn't there be packages like very_cool-software? And some packages are named foo_bar or on PyPI so we should keep the spelling of PyPI although in general it should by hyphens.

yes, we should keep the spelling of PyPI for the extension name. i meant first trying with underscore for the tarball, as the hyphen should normally only be used to separate the name from the version in the tarball.

[jfgrimm]

lgtm