athena error message fix

[martynaut]

Goal of this PR: we have better error messages for Athena API.

AC:

• We always return pandas DataFrame if no filename is defined (even when errors occur)
• We always return None if filename is defined (even when errors occur)
• Printed messages are actionable

Use case for which wrong message was raised:

1. run query similar to one below in a cell (note missing quote on day value)

query = query_athena('''SELECT * FROM table_name WHERE year = '2019' AND month = '09' AND day = '07 limit 10''')

2. returns: Please check your credentials including s3_bucket in config.ini file

When the same query is run in Athena it throws an error line 3:60: no viable alternative at input '= '' (service: amazonathena; status code: 400; error code: invalidrequestexception; request id: 46d71f5e-ac75-4dab-a474-4c9541774386)

TODO in future:

• We plan to add debug mode for all API connectors. If enabled Errors will be raised.

[martynaut]

Added handling of incorrect input to function as suggested by @dorotamierzwa