Do not show internal traceback when validating "parametrize" values

[nicoddemus]

Consider:

import pytest
@pytest.mark.parametrize("x, expected", [(10, 20), (40, 80)], ids=[1,2,3])
def test_ids_numbers(x,expected):
    assert x * 2 == expected

Running this on pytest-3.0.1 produces:

=================================== ERRORS ====================================
______________________ ERROR collecting tmp/test_bug.py _______________________
X:\pytest\_pytest\runner.py:163: in __init__
    self.result = func()
X:\pytest\_pytest\main.py:460: in _memocollect
    return self._memoizedcall('_collected', lambda: list(self.collect()))
X:\pytest\_pytest\main.py:331: in _memoizedcall
    res = function()
X:\pytest\_pytest\main.py:460: in <lambda>
    return self._memoizedcall('_collected', lambda: list(self.collect()))
X:\pytest\_pytest\python.py:405: in collect
    return super(Module, self).collect()
X:\pytest\_pytest\python.py:319: in collect
    res = self.makeitem(name, obj)
X:\pytest\_pytest\python.py:331: in makeitem
    collector=self, name=name, obj=obj)
X:\pytest\_pytest\vendored_packages\pluggy.py:724: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
X:\pytest\_pytest\vendored_packages\pluggy.py:338: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
X:\pytest\_pytest\vendored_packages\pluggy.py:333: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
X:\pytest\_pytest\vendored_packages\pluggy.py:595: in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
X:\pytest\_pytest\vendored_packages\pluggy.py:249: in _wrapped_call
    wrap_controller.send(call_outcome)
X:\pytest\_pytest\python.py:192: in pytest_pycollect_makeitem
    res = list(collector._genfunctions(name, obj))
X:\pytest\_pytest\python.py:351: in _genfunctions
    self.ihook.pytest_generate_tests(metafunc=metafunc)
X:\pytest\_pytest\vendored_packages\pluggy.py:724: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
X:\pytest\_pytest\vendored_packages\pluggy.py:338: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
X:\pytest\_pytest\vendored_packages\pluggy.py:333: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
X:\pytest\_pytest\vendored_packages\pluggy.py:596: in execute
    res = hook_impl.function(*args)
X:\pytest\_pytest\python.py:105: in pytest_generate_tests
    metafunc.parametrize(*marker.args, **marker.kwargs)
X:\pytest\_pytest\python.py:838: in parametrize
    len(argvalues), len(ids)))
E   ValueError: 2 tests specified with 3 ids
!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!
=========================== 1 error in 0.33 seconds ===========================

The error message is correct, but we should prevent that ugly internal traceback to show to users.

[Zac-HD]

================================== test session starts ==================================
platform win32 -- Python 3.6.5, pytest-5.1.3, py-1.7.0, pluggy-0.12.0
collected 0 items / 1 errors

======================================== ERRORS =========================================
_________________________________ ERROR collecting t.py _________________________________
In test_ids_numbers: 2 parameter sets specified, with different number of ids: 3
!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!!!!!
=================================== 1 error in 0.14s ====================================

Not sure when it was fixed, but it's not a problem on Pytest 5.1 😄