BUG hit: "no module named 'grpc.framework'

Summary

We got a stack trace when trying to push an element

[bschubert@me]$ cat 0eae8fd3-push.24630.log
[--:--:--] START   ${ELEMENT}.bst: Push
[--:--:--] LOG     ${ELEMENT}.bst: Build environment for element ${ELEMENT}.bst

    HOME: /tmp
    LC_ALL: C
    LOGNAME: tomjon
    PATH: /usr/bin:/bin:/usr/sbin:/sbin
    SHELL: /bin/sh
    SOURCE_DATE_EPOCH: '1320937200'
    TERM: dumb
    TZ: UTC
    USER: tomjon
    USERNAME: tomjon
[--:--:--] BUG     ${ELEMENT}.bst: Push

    An unhandled exception occured:

    Traceback (most recent call last):
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/_scheduler/jobs/job.py", line 417, in _child_action
        result = self.child_process()  # pylint: disable=assignment-from-no-return
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/_scheduler/jobs/elementjob.py", line 94, in child_process
        return self._action_cb(self._element)
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/_scheduler/queues/pushqueue.py", line 37, in process
        if not element._push():
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/element.py", line 1835, in _push
        pushed = self.__artifacts.push(self, self.__get_cache_keys_for_commit())
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/_artifactcache/artifactcache.py", line 623, in push
        remote.init()
      File "/home/bschubert/.local/lib/python3.6/site-packages/buildstream/_artifactcache/cascache.py", line 1185, in init
        self.channel = grpc.secure_channel('{}:{}'.format(url.hostname, port), credentials)
      File "/home/bschubert/.local/lib/python3.6/site-packages/grpc/__init__.py", line 1675, in secure_channel
        from grpc import _channel  # pylint: disable=cyclic-import
      File "/home/bschubert/.local/lib/python3.6/site-packages/pluginbase.py", line 439, in plugin_import
        fromlist, level)
      File "/home/bschubert/.local/lib/python3.6/site-packages/grpc/_channel.py", line 25, in <module>
        from grpc.framework.foundation import callable_util
      File "/home/bschubert/.local/lib/python3.6/site-packages/pluginbase.py", line 439, in plugin_import
        fromlist, level)
    ModuleNotFoundError: No module named 'grpc.framework'

Launching python and "import grpc.framework" does work. Pushing again did work.

Steps to reproduce

Sadly... no idea

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

Possible fixes

Other relevant information

• BuildStream version affected: /milestone %BuildStream_v1.x

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