add check for http:// URLs in easyconfig files added/changed in PRs

[boegel]

works as expected, see #8999 where I squeezed in this change too by matter of proof of concept...

[boegel]

@Micket Once this is merged, tests in Travis will fail for (new/updated) PRs if easyconfigs still have http:// in them.

We may need to whitelist for some stuff where https:// doesn't work (should we auto-check if the specified URLs exist?)

[Micket]

@boegel Having looked through a bunch of them the past week, I've vaguely recall seeing at least a couple of exceptions already. I think autochecking would be a good idea before requiring it
If they aren't using https, and there is a positive response from requests.get(url, verify=True), then they should prefer it.

[boegel]

@Micket Do you happen to recall an example of an exception, to test with?

[Micket]

https://github.com/easybuilders/easybuild-easyconfigs/pull/8997/files
oh and one from you :)
https://github.com/easybuilders/easybuild-easyconfigs/pull/8990/files
which doesn't have a valid certificate, so this should cover the two basic cases

[boegel]

enhanced test works as expected, see #8999 and #9006

[Micket]

lgtm