Pytest generates warnings when using testinfra wrapper

Running a simple test with the testinfra wrapper generates a pytest warning in the console output. The tests pass/fail correctly and the command exits with a zero status code, but the warning is a little concerning. The warning is:

WP1 None Modules are already imported so can not be re-written: testinfra

Testinfra 1.42 Pytest 3.03 Python 2.7.12 macOS 10.12

$ cat mytest.py
def test_passwd_file(File):
    passwd = File("/etc/passwd")
    assert passwd.contains("root")
    assert passwd.user == "root"
    assert passwd.group == "wheel"
    assert passwd.mode == 0o644

(venv)
$ testinfra -v mytest.py
==================================================================== test session starts =====================================================================
platform darwin -- Python 2.7.12, pytest-3.0.3, py-1.4.31, pluggy-0.4.0 -- /Users/me/testing/venv/bin/python2.7
cachedir: .cache
rootdir: /Users/me/testing, inifile:
plugins: testinfra-1.4.2
collected 1 items

mytest.py::test_passwd_file[local] PASSED

=================================================================== pytest-warning summary ===================================================================
WP1 None Modules are already imported so can not be re-written: testinfra
======================================================== 1 passed, 1 pytest-warnings in 0.04 seconds =========================================================```

[adeleglise]

+1

[wachpwnski]

I get this same issue, even when not running it with Molecule.