Backport PR #5933: fix qt_loader import hook signature

to match PEP 302

closes  #5932

IPython/external/qt_loaders.py

@@ -32,17 +32,17 b' class ImportDenier(object):'
         sys.modules.pop(module_name, None)
         self.__forbidden = module_name
 
-    def find_module(self, mod_name, pth):
-        if pth:
+    def find_module(self, fullname, path=None):
+        if path:
             return
-        if mod_name == self.__forbidden:
+        if fullname == self.__forbidden:
             return self
 
-    def load_module(self, mod_name):
+    def load_module(self, fullname):
         raise ImportError("""
     Importing %s disabled by IPython, which has
     already imported an Incompatible QT Binding: %s
-    """ % (mod_name, loaded_api()))
+    """ % (fullname, loaded_api()))
 
 ID = ImportDenier()
 sys.meta_path.append(ID)