setupext.py 文件源码

def check_requirements(self):
        '''
        If PyQt4/PyQt5 is already imported, importing PyQt5/PyQt4 will fail
        so we need to test in a subprocess (as for Gtk3).
        '''
        try:
            p = multiprocessing.Pool()

        except:
            # Can't do multiprocessing, fall back to normal approach ( this will fail if importing both PyQt4 and PyQt5 )
            try:
                # Try in-process
                msg = self.callback(self)

            except RuntimeError:
                raise CheckFailed("Could not import: are PyQt4 & PyQt5 both installed?")

            except:
                # Raise any other exceptions
                raise

        else:
            # Multiprocessing OK
            try:
                res = p.map_async(self.callback, [self])
                msg = res.get(timeout=10)[0]
            except multiprocessing.TimeoutError:
                p.terminate()
                # No result returned. Probaly hanging, terminate the process.
                raise CheckFailed("Check timed out")
            except:
                # Some other error.
                p.close()
                raise
            else:
                # Clean exit
                p.close()
            finally:
                # Tidy up multiprocessing
                p.join()

        return msg