[TIP] ImportError (No module named 'pytest') - weird coverage and py interaction as a result of tox dependency, manuel triggering it...

[holger krekel]

On Thu, Jul 03, 2014 at 10:40 +0100, Chris Withers wrote:
> On 03/07/2014 09:30, Chris Withers wrote:
> >Hi All,
> >
> >So, with:
> >
> >nosetests --with-xunit --with-cov
> >
> >...I get the following failures on Python 3.* in Linux and Mac:
> >
> >ERROR: Failure: ImportError (No module named 'pytest')
> >
> >Full and nasty traceback here:
> >
> >http://jenkins.simplistix.co.uk/job/testfixtures-virtualenv/PYTHON=3.4,label=linux/333/testReport/junit/nose.failure/Failure/runTest/
> >
> >
> >The weird thing is that if I drop the --with-cov, things work fine.
> 
> Some more digging has revealed something interesting.
> 
> So, by the time the problematic import statement in test_docs.py is
> his, when nose is run --with-cov, sys.modules has 310 keys versus
> the 260 it has when run without --with-cov.
> 
> When run without coverage, they're all the same type:
> 
> (Pdb) set(type(v) for v in sys.modules.values())
> {<class 'module'>}
> 
> When run with coverage, we get a bunch of things:
> 
> (Pdb) set(type(v) for v in sys.modules.values())
> {
> <class 'py._apipkg.ApiModule'>,
> <class 'py._apipkg.AliasModule.<locals>.AliasModule'>,
> <class 'py._apipkg.AliasModule.<locals>.AliasModule'>,
> <class 'module'>,
> <class 'py._apipkg.AliasModule.<locals>.AliasModule'>,
> <class 'py._apipkg.AliasModule.<locals>.AliasModule'>
> }
> 
> ...one of which causes problems when the manuel package's
> introspection tries to do:
> 
>  24  -> def absolute_import(name):
>  25         module_path = normalize_module_path(imp.find_module(name)[1])
>  26
>  27         # don't create a new module object if there's already
> one that we can reuse
>  28         for module in list(sys.modules.values()):
>  29             if module is None or not hasattr(module, '__file__'):
>  30                 continue
>  31             if module_path == normalize_module_path(module.__file__):
>  32                 return module
> 
> (Pdb) hasattr(sys.modules['py.test'], '__file__')
> *** ImportError: No module named 'pytest'
> 
> So, any ideas?

There is some import-machinery-using compatibility code in ``py`` to
make ``py.test`` resolve to ``pytest``.  Maybe some bad interactions 
go on here with coverage but can't dig further at the moment.  You might
check in your own code if anything is using py.test instead of pytest,
but it's probably triggered somewhere else.

holger


> Chris
> 
> -- 
> Simplistix - Content Management, Batch Processing & Python Consulting
>            - http://www.simplistix.co.uk
>