syntax check for modified puppet template and manifests

syntax_check.py

#!/usr/bin/python
import os.path
import subprocess
import sys

def get_modified_files():
    """
    return a list of modified files tracked by git
    """
    git_status = subprocess.Popen(['git', 'status', '-s'], stdout=subprocess.PIPE)
    files, err = git_status.communicate()
    return [f.strip('? MA') for f in files.split('\n')]

def syntax_check(files):
    """
    Perform syntax check towards given files

    arguments:
    files -- a list of modified files
    """
    err_msg = ''

    for file in files:
        # manifest files
        if os.path.splitext(file)[1] == '.pp':
            check_manifest = subprocess.Popen(['puppet','parser','validate',file])
            check_manifest.communicate()

            if check_manifest.returncode != 0:
                err_msg += str(check_manifest.stderr)

        # template files
        if os.path.splitext(file)[1] == '.erb':
            check_template_cmd = "erb -P -x -T '-' %s | ruby -c" % file
            check_template = subprocess.Popen(check_template_cmd, shell=True, stdout=subprocess.PIPE)
            check_template.communicate()

            if check_template.returncode != 0:
                err_msg += str(check_template.stderr)

    return err_msg

if __name__ == '__main__':
    modified_files = get_modified_files()
    output = syntax_check(modified_files)
    if output:
        sys.exit('modified files have syntax error')
    else:
        sys.exit(0)