selenium needs to be pinned to <3 for travis to be able to run integration tests

[peterlauri]

I bumped into this with my private projects, and fixed build issues by pinning selenium<3 in test requirements. Note that tests are failing, but they are not related to this fix. See the build history in by branch, and you can see that first build failed with errors like:

tests/test_plugin.py::test_browser Exception AttributeError: "'Service' object has no attribute 'process'" in <bound method Service.__del__ of <selenium.webdriver.firefox.service.Service object at 0x7f5452531f10>> ignored
Exception AttributeError: "'Service' object has no attribute 'process'" in <bound method Service.__del__ of <selenium.webdriver.firefox.service.Service object at 0x7f5452531250>> ignored
ERROR

---

This change is

[coveralls]

Coverage remained the same at 86.742% when pulling 558a7fd on peterlauri:firefox-problems into 34e2009 on pytest-dev:master.

[coveralls]

Coverage remained the same at 86.742% when pulling 558a7fd on peterlauri:firefox-problems into 34e2009 on pytest-dev:master.

[pelme]

@peterlauri any idea what the root cause is? i guess supporting selenium 3 would be a good thing too. :)

[miohtama]

Without going to the root cause: Selenium 3 with Firefox uses something called Marionette to talk to the browser. Marionette is different beast altogether with different internals, so internal APIs differ. Also it is not yet in-par features wise with Selenium 2, so some existing tests might not run on Marionette.

[pelme]

I see. It broke my own test suite too. :(

Is the general "solution" to just stay on Selenium 2 until geckodriver/marionette reaches some kind of parity with the old driver?

[pelme]

Reviewed 1 of 1 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved, some commit checks failed.

---

Comments from Reviewable

[pelme]

Thanks for figuring this out! I fixed a couple of other problems stole this commit and merged in #80 .