exception message uses max_volume no current_volume

Author: andySigler

opentrons/instruments/pipette.py

@@ -335,7 +335,7 @@ def _setup():
                 raise RuntimeWarning(
                     'Pipette ({0}) cannot hold volume {1}'
                     .format(
-                        self.current_volume,
+                        self.max_volume,
                         self.current_volume + volume)
                 )