.. because I want to make the 'install_and_run' script useful for non-synapse
jobs, which do not accept --python. In any case we set up the path here, so
sytest shouldn't be guessing it.

* Factor out more common code from the jenkins scripts

* Fix install_and_run path

* Poke jenkins

* Poke jenkins

* Factor out some of the code shared between the different sytest jenkins scripts

* Exclude jenkins from the MANIFEST

* Fix dendron build

* Missing new line

* Poke jenkins

* Export the PORT_BASE and PORT_COUNT

* Poke jenkins

Also move the options from the shebang line to the body of the script, so that
they take effect even if somebody explicitly runs "bash jenkins.sh"

Also move the options from the shebang line to the body of the script, so that
they take effect even if somebody explicitly runs "bash jenkins.sh"

So we don't try to checkout a stale ref

Documented by matrix-org/matrix-doc#246

Depends on https://github.com/matrix-org/synapse/pull/380

Outputs:
 * results.xml
 * coverage.xml
 * violations.flake8.log