Cloning into 'working_repo'...
Switched to branch 'autosynth-spanner'
Traceback (most recent call last):
  File "synth.py", line 18, in <module>
    import synthtool.gcp as gcp
  File "/home/kbuilder/.local/lib/python3.6/site-packages/synthtool/gcp/__init__.py", line 15, in <module>
    from . import gapic_generator
  File "/home/kbuilder/.local/lib/python3.6/site-packages/synthtool/gcp/gapic_generator.py", line 22, in <module>
    from synthtool.sources import git
  File "/home/kbuilder/.local/lib/python3.6/site-packages/synthtool/sources/git.py", line 24, in <module>
    from synthtool import metadata
  File "/home/kbuilder/.local/lib/python3.6/site-packages/synthtool/metadata.py", line 22, in <module>
    from synthtool.protos import metadata_pb2
  File "/home/kbuilder/.local/lib/python3.6/site-packages/synthtool/protos/metadata_pb2.py", line 28, in <module>
    dependencies=[google_dot_protobuf_dot_timestamp__pb2.DESCRIPTOR],
TypeError: __new__() got an unexpected keyword argument 'serialized_options'

Synthesis failed