Fix undefined name: import as_str_any for line 35 (#16668)

flake8 testing of https://github.com/tensorflow/tensorflow on Python 2.7.14

$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
```
./tensorflow/python/util/compat_internal.py:33:12: F821 undefined name 'as_str_any'
    path = as_str_any(path.__fspath__())
           ^
```