Fixed unit tests.

Author: Jean-Mathieu Deschenes

pandas/core/dtypes/common.py

@@ -396,7 +396,10 @@ def is_timedelta64_dtype(arr_or_dtype):
 
     if arr_or_dtype is None:
         return False
-    tipo = _get_dtype_type(arr_or_dtype)
+    try:
+        tipo = _get_dtype_type(arr_or_dtype)
+    except ValueError:
+        return False
     return issubclass(tipo, np.timedelta64)