search: provide a better error when regex is incorrect

[yarikoptic]

Although it is quite easy to grasp what went wrong familiar with python

$> datalad search path:*T1w.nii.gz
[ERROR  ] nothing to repeat at position 0 [sre_parse.py:_parse:651] (error)

I think a better error would be

[ERROR ] regular expression '*T1w.nii.gz' is incorrect:  nothing to repeat at position 0 [search.py:...] (error)

which would become especially useful in case of multiple regular expressions and more tricky ones

[adswa]

I think your merged PR that fixed this for some reason did not automatically close this issue? I will close it, please reopen if I'm mistaken here. PS: I like the improved error message :)

[kyleam]

Thanks @adswa

I think your merged PR that fixed this for some reason did not automatically close this issue?

When a PR is based off of a branch other than the default branch of the repo, the closes/fixes cookie needs to be in a commit message, not just the PR description.

[adswa]

Thank you for sharing, I did not know this :)