change imports in cupy module to be local (#1548)

pyqtgraph/functions.py

@@ -15,7 +15,7 @@ import sys
 import warnings
 
 import numpy as np
-from pyqtgraph.util.cupy_helper import getCupy
+from .util.cupy_helper import getCupy
 
 from . import debug, reload
 from .Qt import QtGui, QtCore, QT_LIB, QtVersion

pyqtgraph/util/cupy_helper.py

@@ -1,8 +1,7 @@
 import os
 from warnings import warn
 
-from pyqtgraph import getConfigOption
-
+from .. import getConfigOption
 
 def getCupy():
     if getConfigOption("useCupy"):