import-checker: increase portability for python 2.6.x
Before this patch, fromlocalfunc() assumes that "module" attribute of
ast.ImportFrom is None for "from . import a", and Python 2.7.x
satisfies this assumption.
On the other hand, with Python 2.6.x, "module" attribute of
ast.ImportFrom is an empty string for "from . import a", and this
causes failure of test-check-module-imports.t.
#require unix-permissions no-root
$ hg init a
$ cd a
$ echo foo > b
$ hg add b
$ hg ci -m "b"
$ chmod -w .hg/store
$ cd ..
$ hg clone a b
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +w a/.hg/store # let test clean up
$ cd b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
$ cd ..