RSA public keyfile - TypeError: can only concatenate str (not "bytes") to str

[joeleong]

$ pyadb shell ls
Traceback (most recent call last):
  File "/usr/local/bin/pyadb", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.7/site-packages/adb/adb_debug.py", line 207, in main
    rsa_keys=[rsa_signer(path) for path in args.rsa_key_path])
  File "/usr/local/lib/python3.7/site-packages/adb/common_cli.py", line 151, in StartCli
    **device_kwargs)
  File "/usr/local/lib/python3.7/site-packages/adb/adb_commands.py", line 137, in ConnectDevice
    self._Connect(**kwargs)
  File "/usr/local/lib/python3.7/site-packages/adb/adb_commands.py", line 168, in _Connect
    conn_str = self.protocol_handler.Connect(self._handle, banner=banner, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/adb/adb_protocol.py", line 331, in Connect
    data=rsa_keys[0].GetPublicKey() + b'\0')
TypeError: can only concatenate str (not "bytes") to str

I assume this has to do with python3 compatibility as it seems to work fine on python2.
To repro you can seemingly connect to any device that doesn't already have your public key approved.