Pybrake query notifier throws error when query is a psycopg2 Composed object

[mlennon-spr]

    import pybrake

    notifier = pybrake.Notifier(project_id='test',
                                project_key='test',
                                )
    query = sql.SQL("""
               SELECT
                   1
               WHERE
                   1 in {ids}
               """).format(ids=sql.Literal((1,2,3)))
    notifier.queries.notify(
        query=query,
        method='request.method',
        route='test-route',
        start_time=time.time(),
        end_time=time.time(),
    )

Raises an error: unhashable type: 'Composed':

File "/usr/local/lib/python3.7/site-packages/pybrake/queries.py" in notify
  61.             if key in self._stats:
Exception Value: unhashable type: 'Composed'

This seems to arise because query_stat_key def query_stat_key(*, query="", method="", route="", time=None): is used to create a dictionary key, which would only be valid if the query object is hashable.

[scottsbaldwin]

@shifi can you take a look at this issue and the related PR?