util: disinfect lookup_reg strings (issue1126) lookup_reg could return Unicode strings, which would infect other strings and generate unexpected tracebacks. Spotted by Rémy Roy. Fold in silly nested function while we're at it.

test symlinks on symlink-capable os but non-capable filesystem (issue1149) The "real" way to test this is to mount a non-symlink-capable filesystem, and try working on it; however, I don't know how to mount filesystems as a non-priveleged user from within the testing framework. So instead, os.symlink is overridden to raise the exception that would be raised on such a filesystem.