Merge pull request #2983 from nicoddemus/improve-assert-2979

Improve getscopeitem assertion message

Author: RonnyPfannschmidt

_pytest/fixtures.py

@@ -553,7 +553,7 @@ def _getscopeitem(self, scope):
         if node is None and scope == "class":
             # fallback to function item itself
             node = self._pyfuncitem
-        assert node
+        assert node, 'Could not obtain a node for scope "{}" for function {!r}'.format(scope, self._pyfuncitem)
         return node
 
     def __repr__(self):