[modutils] Fix modutils.modpath_from_file (closes #100757)

1                                if pkg]
2                  if _check_init(path, submodpath[:-1]):
3                      return extrapath[path_].split('.') + submodpath
4      for path in sys.path:
5          path = abspath(path)
6 -        if path and base[:len(path)] == path:
7 -            if path.startswith(EXT_LIB_DIR):
8 -                continue
9 +        if path and base.startswith(path):
10              modpath = [pkg for pkg in base[len(path):].split(os.sep) if pkg]
11              if _check_init(path, modpath[:-1]):
12                  return modpath
13      raise ImportError('Unable to find module for %s in %s' % (
14          filename, ', \n'.join(sys.path)))