usb1: Fix exception raised during handleEvents.

Fixes errors like:
    File "usb1/__init__.py", line 2375, in handleEvents
      self.__mayRaiseUSBError(
    File "usb1/__init__.py", line 127, in mayRaiseUSBError
      if value < 0:
  TypeError: '<' not supported between instances of 'USBContext' and 'int'

Author: vpelletier

usb1/__init__.py

@@ -2079,7 +2079,7 @@ class USBContext:
     __poll_cb_user_data = None
     __auto_open = True
     __has_pollfd_finalizer = False
-    __mayRaiseUSBError = mayRaiseUSBError
+    __mayRaiseUSBError = staticmethod(mayRaiseUSBError)
     __libusb_handle_events = None
 
     # pylint: disable=no-self-argument,protected-access