Given a list of commands, runCommands executes them.
        This is one of the two key methods of MapExecutor.

def runCommands(self,commands,args):
        """
        Given a list of commands, runCommands executes them.
        This is one of the two key methods of MapExecutor.
        """
        errorCounter = 0
        if args.list:
            print '\n'.join(commands)
        else:
            # Each command is executed sequentially:
            for command in commands:
                process = subprocess.Popen(command, stdout=subprocess.PIPE,stderr=subprocess.PIPE,shell=True)
                stream = process.communicate()
                output = stream[0]
                erroroutput = stream[1]
                returncode = process.returncode
                if args.verbose:
                    print 'Executing command: '+command
                if returncode != 0:
                    errorCounter = errorCounter + 1
                    if args.verbose or not args.ignore_errors:
                        print 'An error occurred:\n'
                        print erroroutput
                    if not args.ignore_errors:
                        print('Terminating map process.')
                        break
                if returncode == 0 and len(output) > 0:
                    sys.stdout.write(output)
        if args.verbose:
            print 'Process completed successfully.'
            if errorCounter > 0:
                if errorCounter > 1:
                    print str(errorCounter) + ' errors occurred during the process.'
                else:
                    print str(errorCounter) + ' error occurred during the process.'