Added pass.

gprMax/exceptions.py

@@ -17,4 +17,5 @@
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
 class CmdInputError(ValueError):
-    """Handles errors in user specified commands. Subclasses the ValueError class."""
+    """Handles errors in user specified commands. Subclasses the ValueError class."""
+    pass