Now I got this error. It seems that I should pin the version of importlib-metadata?

No cached artifacts for 254 targets.
                   Invalidated 254 targets.14:03:36 [WARN] /home/cedriczheng/.cache/pants/setup/bootstrap-Linux-x86_64/1.23.0_py36/lib/python3.6/site-packages/pex/pep425tags.py:274: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp

**** Failed to install importlib_metadata-4.11.3 (caused by: NonZeroExit("received exit code 1 during execution of `['/usr/bin/python2.7', '-s', '-', 'bdist_wheel', '--dist-dir=/tmp/tmpwfro9psz']` while trying to execute `['/usr/bin/python2.7', '-s', '-', 'bdist_wheel', '--dist-dir=/tmp/tmpwfro9psz']`",)
):
stdout:

stderr:
Traceback (most recent call last):
  File "<stdin>", line 13, in <module>
IOError: [Errno 2] No such file or directory: 'setup.py'



               Waiting for background workers to finish.
07:03:38 00:04   [complete]
               FAILURE