warning that duecredit is not installed when loading package

[kain88-de]

Expected behaviour

no warning when loading the module

Actual behaviour

warning that duecredit is not installed.

Currently version of MDAnalysis:

(run python -c "import MDAnalysis as mda; print(mda.__version__)")
0.18.0

[orbeckst]

I thought we had taken care of this as part of PR #1822 , specifically e3d5cac but it seems we have to revisit.

[orbeckst]

For the record (using Python 3.6 on macOS) in a conda environment without duecredit gives:

cat > credit.py << 'EOF'
import MDAnalysis
print(MDAnalysis.__version__)
EOF
python credit.py

gives

/[...]/mdanalysis/package/MDAnalysis/due.py:88: UserWarning: No module named 'duecredit'
  warnings.warn(str(err))
0.18.1-dev

[orbeckst]

It raises a ModuleNotFoundError: No module named 'duecredit' (since Python 3.6). Will patch it. Not sure how to test it in our current testing framework because the due.py code is run on the very first import of MDAnalysis. Maybe mock duecredit and re-import MDAnalysis.due... suggestions welcome.

EDIT: removed stuff on how I was to dumb to check if ModuleNotFoundError is an instance of ImportError.

[richardjgowers]

@orbeckst we used to have some tests that tested for deprecation warnings or something, I think we deleted the dict entry from sys.modules and that forced the reload of the module

[orbeckst]

Btw, the Python docs say https://docs.python.org/3/library/exceptions.html#ModuleNotFoundError

exception ModuleNotFoundError

A subclass of ImportError which is raised by import when a module could not be located. It is also raised when None is found in sys.modules.

New in version 3.6.

The following does catch that ModuleNotFoundError

In [12]: try:
    ...:     raise ModuleNotFoundError("foo")
    ...: except ImportError as err:
    ...:     print("Import error", err)
    ...:
Import error foo

[orbeckst]

I just can't read code anymore... the exceptions work as they should, I just have to remove the debugging code :-p

mdanalysis/package/MDAnalysis/due.py

Line 88 in 8c331d7

warnings.warn(str(err))

[mimischi]

I'm still getting the same warning with MDAnalysis 0.18.0 in a fresh environment:

$ python -c "import MDAnalysis as mda; import sys; print(mda.__version__); print(sys.version);"
/home/mischi/.virtualenvs/test-oN5qujzB/lib/python3.6/site-packages/MDAnalysis/due.py:88: UserWarning: No module named 'duecredit'
  warnings.warn(str(err))
0.18.0
3.6.5 (default, Apr 14 2018, 13:17:30) 
[GCC 7.3.1 20180406]

[kain88-de]

This error is fixed in the next release

[Ruibin-Liu]

I first saw the same warning. But after I install the duecredit package, the warning message disappears. I guess the package dependencies are not right?

[richardjgowers]

@rainbeeliu the dependencies are correct in that duecredit isn't necessary for the package to function. You only need duecredit for duecredit (citation) things.