message: Use pip directly; use RUNFILES_MANIGEST_FILE
diff: @@ -22,9 +22,12 @@ def _find_in_runfiles(logical_name):
  return _find_in_runfiles.manifest.get(key, logical_name)
  except AttributeError:
  _find_in_runfiles.manifest = {}
  - if 'RUNFILES_DIR' in os.environ:
  + manifest_filename = None
  + if 'RUNFILES_MANIFEST_FILE' in os.environ:
  + manifest_filename = os.environ['RUNFILES_MANIFEST_FILE']
  + elif 'RUNFILES_DIR' in os.environ:
  manifest_filename = os.path.join(os.environ['RUNFILES_DIR'], 'MANIFEST')
  - if os.path.exists(manifest_filename):
  + if manifest_filename and os.path.exists(manifest_filename):
  with open(manifest_filename) as manifest:
  for line in manifest:
  (logical, physical) = line.split(' ', 2)
  @@ -61,7 +64,7 @@ class VirtualEnv(object):
  check_call(['virtualenv'] + vpython + VENV_ARGS + [self._path])
  for requirement in self._requirements:
  check_call(
  - [self.python, self._pip, 'install', '-r',
  + [self._pip, 'install', '-r',
  _find_in_runfiles(requirement)])
  except:
  if os.path.exists(self._path):
  