Toolbox in ArcGIS Python Add-In

01-original.py

import arcpy
import pythonaddins

class addDefinitionQueryLayers(object):
"""Implementation for arcpyMappingAddin_addin.button (Button)"""

  def __init__(self):
    self.enabled = True
    self.checked = False

  def onClick(self):
    pass

02-modified.py

import arcpy
import pythonaddins
import os.path

class addDefinitionQueryLayers(object):
"""Implementation for arcpyMappingAddin_addin.button (Button)"""

  def __init__(self):
      self.enabled = True
      self.checked = False

  def onClick(self):
    # name of toolbox without tbx extension
    toolboxName = "Mapping"

    # name of tool to be executed
    toolName = "AddDefinitionQueryLayers"

    # create string with path to toolbox
    toolboxPath = os.path.join(os.path.dirname(__file__), toolboxName + ".tbx")

    # call geoprocessing tool
    pythonaddins.GPToolDialog(toolboxPath, toolName)