/opt/eff.org/certbot/venv/bin/python: No module named pip.__main__; 'pip' is a package and cannot be directly executed
Traceback (most recent call last):
  File "/tmp/tmp.xopGpEgDgY/pipstrap.py", line 177, in <module>
    sys.exit(main())
  File "/tmp/tmp.xopGpEgDgY/pipstrap.py", line 149, in main
    pip_version = StrictVersion(check_output([python, '-m', 'pip', '--version'])
  File "/usr/lib/python2.7/subprocess.py", line 544, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '['/opt/eff.org/certbot/venv/bin/python', '-m', 'pip', '--version']' returned non-zero exit status 1