Use dev pytest version in verification

[kevinsung]

The latest version of pytest fails with

_________________________________________ test_deprecated_test __________________________________________

    @deprecated_test
    def test_deprecated_test():
        warnings.simplefilter('error')
>       f()

_compat_test.py:51: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

args = (), kwargs = {}, cls = <class 'deprecation.DeprecatedWarning'>
the_warning = DeprecatedWarning('f', None, None, '')

    @functools.wraps(function)
    def _inner(*args, **kwargs):
        if should_warn:
            if is_unsupported:
                cls = UnsupportedWarning
            else:
                cls = DeprecatedWarning
    
            the_warning = cls(function.__name__, deprecated_in,
                              removed_in, details)
            warnings.warn(the_warning, category=DeprecationWarning,
>                         stacklevel=2)
E           deprecation.DeprecatedWarning: f is deprecated

[viathor]

IIUC, you need this to proceed with your work on the new release, so I'm approving, but I am concerned about this change, because the problem you're seeing means we won't be able to update pytest until this is resolved. Could you file an issue so we don't loose track of it?

[kevinsung]

Filed #380