import subprocess

class CommandError(subprocess.CalledProcessError):
        def __init__(self,retcode,command,output):
                subprocess.CalledProcessError.__init__(self,retcode,command)
                self.output=output
        def __str__(self):
             return "Command '%s' returned non-zero exit status %d:\n%s" % (self.cmd, self.returncode,self.output)

def execute(command, ignore_error = False, fork = False ):
	stdout = subprocess.PIPE
	stderr = subprocess.STDOUT	
	if fork:
		stdout = None
		stderr = None
        process=subprocess.Popen(command,stdout=stdout,stderr=stderr,shell=True, universal_newlines = True,executable="/bin/bash")
	if fork:
		return None
        output = process.communicate()
        retcode = process.poll()
        if retcode and not ignore_error:
                raise CommandError(retcode, command, output[0])
        return output