DeprecationWarning for imp module triggered when run with -Werror

[johnthagen]

Testing with -Werror is convenient for CI testing so that warnings can be quickly identified and corrected rather than staying dormant.

With Python 3.5.1 if you execute with -Werror you receive a PendingDeprecationWarning because imp has been deprecated since Python 3.4.

Edit: As of Python 3.6 this is now a full DeprecationWarning.

The code causing the issue is:

pytest/src/_pytest/assertion/rewrite.py

Line 8 in ecc5c84

import imp

To reproduce:

$ python -Werror -m pytest test.py

Traceback (most recent call last):
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\pytest.py", line 16, in <module>
    import pytest
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\pytest.py", line 27, in <module>
    _preloadplugins() # to populate pytest.* namespace so help(pytest) works
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\_pytest\config.py", line 75, in _preloadplugins
    _preinit.append(get_config())
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\_pytest\config.py", line 84, in get_config
    pluginmanager.import_plugin(spec)
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\_pytest\config.py", line 384, in import_plugin
    __import__(importspec)
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\site-packages\_pytest\main.py", line 6, in <module>
    import os, sys, imp
  File "C:\Users\John Hagen\AppData\Local\Programs\Python\Python35\lib\imp.py", line 33, in <module>
    PendingDeprecationWarning, stacklevel=2)
PendingDeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses

$ pip -V
pip 8.0.2
$ pip list
...
pytest (2.8.7)

This was tested on Windows 10 x64.

[RonnyPfannschmidt]

closing this one,
the remaining import of the imp module is in a place that handles old python versions

[rpkilby]

@RonnyPfannschmidt - is there an alternative way to view deprecations with pytest? The -Wall and Wonce flags aren't sufficient, since they only report the last line of the stack trace. Usually, you would use -Werror, however this causes the test runner to break before the test suite can even run.

As a side note, This now affects the assertion.rewrite module.

[rpkilby]

the remaining import of the imp module is in a place that handles old python versions

If the code is only handling old python versions, why is it executing in python 3.5?

[RonnyPfannschmidt]

@rpkilby mainly because the code is in place and the import didnt hurt anyone before

[nicoddemus]

If the code is only handling old python versions, why is it executing in python 3.5?

It is used by all Python versions actually. In order to get rid of it we have to map the functionality used by imp to importlib (its replacement) and create a compatibility layer because importlib was introduced in 3.1 only.

[rpkilby]

Thanks @RonnyPfannschmidt & @nicoddemus.
For anyone else who runs into this, there is pytest-warnings which seems to work well enough.

[nicoddemus]

Closing this because I don't think there's any explicit action left to be done here

[leezu]

Shouldn't this stay open until the compatibility layer mentioned by @nicoddemus is introduced?

With

This is pytest version 3.2.2, imported from /usr/lib64/python3.6/site-packages/pytest.py
setuptools registered plugins:
  pytest-timeout-1.2.0 at /usr/lib64/python3.6/site-packages/pytest_timeout.py
  pytest-pep8-1.0.6 at /usr/lib64/python3.6/site-packages/pytest_pep8.py
  pytest-cov-2.5.1 at /usr/lib64/python3.6/site-packages/pytest_cov/plugin.py

_pytest/assertion/rewrite.py uses the imp module, triggering the following warning on every run of one of my programs:

/usr/lib64/python3.6/site-packages/_pytest/assertion/rewrite.py:7: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp            

which I think is annoying enough to at least leave the report open ;)?

[nicoddemus]

@leezu thanks that's a good point.