def execute_no_wait(self, cmd, walltime, envs={}):
current_env = copy.deepcopy(self._envs)<EOL>current_env.update(envs)<EOL>try:<EOL><INDENT>proc = subprocess.Popen(<EOL>cmd,<EOL>stdout=subprocess.PIPE,<EOL>stderr=subprocess.PIPE,<EOL>cwd=self.userhome,<EOL>env=current_env,<EOL>shell=True,<EOL>preexec_fn=os.setpgrp<EOL>)<EOL>pid = proc.pid<EOL><DEDENT>except Exception as e:<EOL><INDENT>logger.warn("<STR_LIT>", (cmd, e))<EOL>raise<EOL><DEDENT>return pid, proc<EOL>
Synchronously execute a commandline string on the shell.

        Args:
            - cmd (string) : Commandline string to execute
            - walltime (int) : walltime in seconds, this is not really used now.

        Returns a tuple containing:

           - pid : process id
           - proc : a subprocess.Popen object

        Raises:
         None.