Short PR to improve some things during snap builds:
* cleanup snapcraft assets before a build, in order to avoid some weird errors when two builds are executed consecutively without cleanup
* use python3 explicitly in `tools/simple_http_server.py` because on several recent distributions, `python` binary is not exposed anymore, only `python2` or `python3`.
Fixes#6955.
This updates the Fedora version used in our test farm tests to Fedora 30. The AMI ID comes from https://alt.fedoraproject.org/cloud/ where it is listed as their standard HVM AMI for the region we use us-east-1 (US East (N. Virginia)).
Unfortunately, there were a lot of small changes required for this. The big reason for this is on Fedora, there isn't a Python 2 executable installed. In fact, there's not even an executable named python. It's just python3. Rather than installing another Python in each test, I wrote a script that the test scripts can share to figure out the different paths and names that should be used in their script. (This isn't used in test_sdists.sh because the logic is a little different.)
Other changes here worth flagging are:
I changed the name of the variable RUN_PYTHON3_TESTS in test_leauto_upgrades.sh to RUN_RHEL6_TESTS. The tests that are run when this variable is set test the upgrade from Python 2 to Python 3 on RHEL 6. I think this new name is much better now that we also have Fedora running Python 3.
I made tools/simple_http_server.py work on Python 3.
You can see tests passing with these changes at https://travis-ci.com/certbot/certbot/builds/113821476. I also ran test_tests.sh and they passed.
* Update to Fedora 30 in test farm tests.
Fedora 28 is likely to reach its EOL soon.
* Add set_python_envvars.sh.
* Fix test_apache2.sh on python3 only distros.
* Fix test_leauto_upgrades.sh on python3 systems.
* Fix certonly_standalone tests with python3 only
* Fix test_sdists.sh on python3 only distros.
* Make simple_http_server.py work on Python 3.
* add comments
* Make leauto_upgrades do a real upgrade
* Cleanup vars and output
* Sleep until the server is ready
* add simple_http_server.py
* Use a randomly assigned port
* s/realpath/readlink
* wait for server before getting port
* s/localhost/all interfaces
