UserAgent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36

Steps to reproduce the problem:
1. I am building the chrome in windows7 
2. Followed the steps from the https://github.com/v8/v8/wiki/Building%20from%20Source
3. after running the command 
python v8gen.py x64.release

Not able to proceed after this step.

What is the expected behavior?

What went wrong?
Hint: You can raise verbosity (-vv) to see the output of failed commands.

Traceback (most recent call last):
  File "v8gen.py", line 304, in <module>
    sys.exit(gen.main())
  File "v8gen.py", line 298, in main
    return self._options.func()
  File "v8gen.py", line 166, in cmd_gen
    gn_outdir,
  File "v8gen.py", line 208, in _call_cmd
    stderr=subprocess.STDOUT,
  File "C:\Users\eresh.kangal\Downloads\Chrome\depot_tools\python276_bin\lib\subprocess.py", line 573, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '['C:\\Users\\eresh.kangal\\Downloads\\Chrome\\depot_tools\\python276_bin\\python.exe', '-u', 'tools\\mb\\mb.py', 'gen', '-f', 'infra\\mb\\mb_conf
ig.pyl', '-m', 'developer_default', '-b', 'x64.release', 'out.gn/x64.release']' returned non-zero exit status 1

Did this work before? N/A 

Chrome version: 55.0.2883.87  Channel: stable
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: Shockwave Flash 24.0 r0