Before this was only done at the time the assertion plugin was loaded.
This lead to counter-intuitive behaviour where two subdirectories with
a pytest_assertrepr_compare hook in their conftest.py would not work,
only one would ever be used.
This defers assiging the _pytest.assertion.util._reprcompare function
until the item is loaded (pytest_runtest_setup) so that it can use the
hookrelay of the test item to find the appropriate
pytest_assertrepr_compare hook for the item.
This fixes issue #77.
Use load_module on the import hook to load the rewritten module. This allows the
removal of the complicated code related to copying pyc files in and out of the
cache location. It also plays more nicely with parallel py.test processes like
the ones found in xdist.
This simply uses difflib to compare the text without the offending
string to the full text.
Also ensures the summary line uses all space available. But the
terminal width is still hardcoded.