fix invalid syntax

[rudehn]

This is invalid syntax and is causing a revert of all new PRs. Fixing this should allow all new PRs to no longer be reverted.

[Ayyko]

https://www.python.org/dev/peps/pep-3107/#return-values What is getting mad about this?

[rudehn]

SyntaxError: invalid syntax
  File "./lib/db.py", line 23
    def create_adapter(adapter_name, config) -> AbstractAdapter:
                                             ^
SyntaxError: invalid syntax

File "./lib/db_adapters/interface.py", line 7
    class AbstractAdapter(object, metaclass=abc.ABCMeta):
                                           ^
SyntaxError: invalid syntax

If it doesn't like it, it doesn't like it

[mdcfe]

$ flake8
./lib/db.py:7:1: F401 'lib.db_adapters.interface.AbstractAdapter' imported but unused

[Ayyko]

¯\_(ツ)_/¯ fair enough

[chaosbot]

:ok_woman: PR passed with a vote of 9 for and 0 against, a weighted total of 8.5 and a threshold of 6.6, and a current meritocracy review.

See merge-commit c83b3697651490b8b9218cd5cc1e2acb0dbfe5e1 for more details.