import-checker: allow symbol imports from mercurial.pycompat Currently, the source transformer inserts `from mercurial.pycompat import delattr, getattr, hasattr, setattr, open, unicode` to the top of every file. As part of getting rid of the source transformer, we'll need to have source code call these wrappers directly. Rather than rewrite all call sites to call pycompat.*, I think it makes sense to import needed symbols via explicit imports. That requires loosening the import checker to allow this. Differential Revision: https://phab.mercurial-scm.org/D7004