v5 breaks Mocha's --require option

[nwoltman]

Mocha's --require option is used to load modules, meaning both local files and modules in node_modules. The changes in fd4b0c5 break this functionality because this line only allows local files to be required (since grunt.file.expand only looks for local files using a glob).

[pocesar]

alright, it was implemented because of #47, I'll try to resolve the path before trying to expand it.
i'll release 5.0.1 shortly

EDIT: actually I missed the nonull option, in the other expand cases I already used it. my bad