message: add tip length to pip object
diff: @@ -14,7 +14,6 @@ class PipetteTip:
  self.length = length
  # This should come from configuration if tip length is not already in db
  -DEFAULT_TIP_LENGTH = 53.2
  class Pipette:
  """
  @@ -97,6 +96,8 @@ class Pipette:
  self.attached_tip = None
  self.instrument_actuator = None
  self.instrument_mover = None
  + self.DEFAULT_TIP_LENGTH = 53.2
  +
  if not name:
  name = self.__class__.__name__
  @@ -769,7 +770,7 @@ class Pipette:
  for i in range(int(presses) - 1):
  self.move_to(self.current_tip().top(tip_plunge), strategy='direct')
  self.move_to(self.current_tip().top(0), strategy='direct')
  - self._add_tip(DEFAULT_TIP_LENGTH)
  + self._add_tip(self.DEFAULT_TIP_LENGTH)
  self.instrument_mover.home()
  return self
  @@ -836,7 +837,7 @@ class Pipette:
  self.current_volume = 0
  self.current_tip(None)
  - self._remove_tip(DEFAULT_TIP_LENGTH)
  + self._remove_tip(self.DEFAULT_TIP_LENGTH)
  return self
  return _drop_tip(location)
  