Fix Travis. Move to travis-ci.com

[mauritsvanrees]

I have migrated this repository to travis-ci.com. See also https://docs.travis-ci.com/user/migrate/open-source-repository-migration. I have updated a few links in our docs.

I triggered a build but it failed with a version conflict:

Version and requirements information containing chardet:
416  Requirement of zest.releaser[recommended]: chardet
417  Requirement of requests: chardet<3.1.0,>=3.0.2
418While:
419  Installing script.
420Error: There is a version conflict.
421We already have: chardet 4.0.0
422but requests 2.22.0 requires 'chardet<3.1.0,>=3.0.2'.

Might be fixable with minor version updates, but I decided to try the latest versions, as far as compatible. We may still want to move completely to pip instead of buildout at some point, and have a saner test setup, maybe with pytest. But for now, this hopefully fixes the tests for a while.

Note, locally, bin/test -t utils.txt succeeds, but a few utils.txt tests fail when run together with all others. First failure:

File "/Users/maurits/tools/src/zest.releaser/zest/releaser/tests/utils.txt", line 423, in utils.txt
Failed example:
    utils.show_interesting_lines(output)
Differences (ndiff with -expected +actual):
    + RED a
    + b
    + c
    + d
    + e
    + f
    + g
    + h
    + i
    + j
    + k
    + l
    + m
    + n
    + Question: There were errors or warnings. Are you sure you want to continue? (y/N)? 
    + Our reply: <ENTER>
      Traceback (most recent call last):
    - ...
    - SystemExit: 1
    +   File "/Users/maurits/.pyenv/versions/3.7.9/lib/python3.7/doctest.py", line 1337, in __run
    +     compileflags, 1), test.globs)
    +   File "<doctest utils.txt[120]>", line 1, in <module>
    +     utils.show_interesting_lines(output)
    +   File "/Users/maurits/tools/src/zest.releaser/zest/releaser/utils.py", line 554, in show_interesting_lines
    +     sys.exit(1)
    +   File "/Users/maurits/tools/src/zest.releaser/zest/releaser/tests/functional.py", line 36, in _exit
    +     raise RuntimeError(msg)
    + RuntimeError: SYSTEM EXIT (code=1)

Travis meanwhile passes on Python 2.7, but fails for all others, so this is work in progress.

[mauritsvanrees]

Only PyPy fails now, some weird version conflict that is raised while getting the hooks:

File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/tests/functional-with-hooks.txt", line 61, in functional-with-hooks.txt
550Failed example:
551    prerelease.main()
552Exception raised:
553    Traceback (most recent call last):
554      File "/opt/python/pypy2.7-7.1.1/lib-python/2.7/doctest.py", line 1315, in __run
555        compileflags, 1) in test.globs
556      File "<doctest functional-with-hooks.txt[12]>", line 1, in <module>
557        prerelease.main()
558      File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/prerelease.py", line 110, in main
559        prereleaser.run()
560      File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/baserelease.py", line 420, in run
561        self._run_hooks('before')
562      File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/baserelease.py", line 417, in _run_hooks
563        utils.run_hooks(self.setup_cfg, which_releaser, when, self.data)
564      File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/utils.py", line 685, in run_hooks
565        run_entry_points(which_releaser, when, data)
566      File "/home/travis/build/zestsoftware/zest.releaser/zest/releaser/utils.py", line 699, in run_entry_points
567        plugin = entrypoint.load()
568      File "/home/travis/virtualenv/pypy2.7-7.1.1/site-packages/pkg_resources/__init__.py", line 2442, in load
569        self.require(*args, **kwargs)
570      File "/home/travis/virtualenv/pypy2.7-7.1.1/site-packages/pkg_resources/__init__.py", line 2465, in require
571        items = working_set.resolve(reqs, env, installer, extras=self.extras)
572      File "/home/travis/virtualenv/pypy2.7-7.1.1/site-packages/pkg_resources/__init__.py", line 791, in resolve
573        raise VersionConflict(dist, req).with_context(dependent_req)
574    ContextualVersionConflict: (typing 3.6.6 (/home/travis/virtualenv/pypy2.7-7.1.1/site-packages), Requirement.parse('typing>=3.7.4'), set(['typing-extensions']))

Meanwhile, I have edited the Travis settings to not run on branches, but only on pull requests. And I have enabled a monthly build.

[mauritsvanrees]

It is green! @reinout do you want to have a look?