Show real error if module exists but import failed

[2xsaiko]

If a module exists but errors during importing (e.g. a bad import inside the module itself) it will act as if the module doesn't exist, which is pretty confusing. In this case propagate the real error.

(Should this unconditionally fail instead of soft-failing when required is False?)

[eli-schwartz]

If a module exists but errors during importing (e.g. a bad import inside the module itself)

Under what circumstances has this been occurring for you?

[2xsaiko]

While working on #14121 and having a bad import in the file :)