Replace prints with logger calls.

[jait]

Description

Replace prints with logger calls. Using print() is bad in frameworks and libraries because then there is no way for the application to control the logging. These prints ended up always in CloudWatch logs, no matter what logging level was used.

[coveralls]

Coverage increased (+0.006%) to 74.351% when pulling 9843613f32995c8d5fb0947fb730d8c6f8b17b3a on jait:fix/logging-prints into 048fbe49050b572c7f04d82c15d8fe32ceb6236a on zappa:master.

[monkut]

It looks like there are a lot of remaining prints in the codebase, can you look into and handle what you can in this PR?

[hellno]

hi @jait, just going through open PRs and doing some housekeeping. Do you want to convert the prints in the codebase into logger calls? If you have any questions, happy to chat here or in Zappa Slack to get this done.