pin dependency awesome_print to v1.7.0 to avoid bug in v1.8.0

[yaauie]

The awesome_print release v1.8.0 contains a bug that causes the Logstash
process to crash while loading if an exception is raised while the library
attempts to load its user-defined defaults from disk (this can occur if the
HOME environment variable is unset, or if the JVM fails to read the file
at ${HOME}/.aprc).

While the bug has been fixed on the awesome_print master branch, until
a release is rolled, pin our dependency to an earlier version to avoid the
bug.

A release of the fix upstream has been requested on 2018-05-02 via
awesome-print/awesome_print#338

[jakelandis]

It seems the difference between 1.7.0 and 1.8.0 is pretty large. Pinning to the elder version may fix this issue, but it also may introduce other issues that may have been fixed:

awesome-print/awesome_print@v1.7.0...v1.8.0

There is outstanding issue in the stdout plugin with workaround:

logstash-plugins/logstash-output-stdout#11

This only happens when run as a service and trying to use this debug. I would prefer to keep the version un-pinned and refer people to work around until the upstream gets fixed.

[guyboertje]

I went through all the changes between 1.7.0 and 1.8.0.
There are plenty of changes to the internal code as cleanup.
There are some changes to formatters for Sequel, Rails and Object instances - none of which apply to our constrained set to allowable Event datatypes.
There are some changes to the formatters for a Ruby Hash but these display using the key: value format which is less familiar than the key => value format as recognised from the LS config.

My opinion is: its OK to pin this gem to 1.7.0 as long as we have a plan to replace awesome_print with our own formatter.

[guyboertje]

LGTM - I think the risks are few in doing this.

[guyboertje]

Another rationale...
LS 2.X up to 5.4.1 used awesome_print v 1.7.0 without issue and the Event became constrained at v5.

[imajes]

Hey guys! I know this is merged etc, but if you still use ap for formatting in logstash, it'd be great to see how version 2.0.0.pre works out for you! :D