Raise specific MarkerError rather than generic ValueError

--HG--
branch : issue463

_pytest/mark.py

@@ -1,6 +1,9 @@
 """ generic mechanism for marking and selecting python functions. """
 import py
 
+class MarkerError(Exception):
+    """Error in use of a pytest marker/attribute"""
+
 
 def pytest_namespace():
     return {'mark': MarkGenerator()}

_pytest/python.py

@@ -4,7 +4,7 @@ import py
 import inspect
 import sys
 import pytest
-from _pytest.mark import MarkDecorator
+from _pytest.mark import MarkDecorator, MarkerError
 from py._code.code import TerminalRepr
 
 import _pytest
@@ -144,8 +144,8 @@ def pytest_cmdline_main(config):
 def pytest_generate_tests(metafunc):
     # this misspelling is common - raise a specific error to alert the user
     if hasattr(metafunc.function, 'parameterize'):
-        msg = "{0} has mark 'parameterize', spelling should be 'parametrize'"
+        msg = "{0} has 'parameterize', spelling should be 'parametrize'"
-        raise ValueError(msg.format(metafunc.function.__name__))
+        raise MarkerError(msg.format(metafunc.function.__name__))
     try:
         markers = metafunc.function.parametrize
     except AttributeError:

testing/python/metafunc.py

@@ -704,7 +704,7 @@ class TestMetafuncFunctional:
         reprec = testdir.inline_run('--collectonly')
         failures = reprec.getfailures()
         assert len(failures) == 1
-        expectederror = "ValueError: test_foo has mark 'parameterize', spelling should be 'parametrize'"
+        expectederror = "MarkerError: test_foo has 'parameterize', spelling should be 'parametrize'"
         assert expectederror in failures[0].longrepr.reprcrash.message