eb does not throw an error if sources are missing

[cmeesters]

Hi,

when there are no sources in a particular easyconfig (e.g. a typo in the sources or source url lists) eb states in the log that nothing could be found, proceeds and throws an error upon the sanity check stage. That merits improvement, doesn't it?

I would like eb to abort when there are zero valid sources.

Opinions?

Best regards,
Christian

[boegel]

@cmeesters There are situations where having no sources at all is valid, for example when installing a toolchain (see the easyconfigs in https://webappsx.ugent.be/eventManager/events/pretrefopenfoamhpc) or when installing a bundle (see for example https://github.com/easybuilders/easybuild-easyconfigs/blob/master/easybuild/easyconfigs/g/GCC/GCC-9.1.0-2.32.eb).

That said, this doesn't mean there isn't any room for improvement, since most installations do involve a non-empty sources list, of course...

Maybe we could print a warning when sources is empty, and simply silence that warning when either the Toolchain, Bundle or PythonBundle easyblocks are used?