[Checkins] [zopefoundation/zope.exceptions] b6b992: Make the flake8 job use a separate cache

[Marius Gedminas]

  Branch: refs/heads/flake8
  Home:   https://github.com/zopefoundation/zope.exceptions
  Commit: b6b992059541a9f3c559ebbe67d70f3041129790
      https://github.com/zopefoundation/zope.exceptions/commit/b6b992059541a9f3c559ebbe67d70f3041129790
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2020-04-10 (Fri, 10 Apr 2020)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Make the flake8 job use a separate cache

The CACHE_NAME environment variable hack is recommended by
https://docs.travis-ci.com/user/caching/

Also, AFAIU the before_cache: rm pip/debug.log is needed only if you
manually try to cache the ~/.cache/pip directory, and shouldn't be
needed for cache: pip.

Also I like 2-space indents in YAML files so there.