[py] Define stdin for service subprocess (#4503)

Author: Melroy van den Berg

py/selenium/webdriver/common/service.py

@@ -71,7 +71,9 @@ def start(self):
             cmd.extend(self.command_line_args())
             self.process = subprocess.Popen(cmd, env=self.env,
                                             close_fds=platform.system() != 'Windows',
-                                            stdout=self.log_file, stderr=self.log_file)
+                                            stdout=self.log_file,
+                                            stderr=self.log_file,
+                                            stdin=PIPE)
         except TypeError:
             raise
         except OSError as err: