This fixes two issues that were prevent pipelines from running:
Use ubuntu 18.04 in pipelines so we can test python 3.4 (no longer present in ubuntu-latest), which we need to support.
Fix new failing health check in hypothesis tests by requiring an old version of hypothesis.
Regarding the old version of hypothesis:
The newer versions require adding a specific health check to a skip list, otherwise many tests fail. But those hypothesis versions don't run on python 3.4, so the pipelines end up using an older hypothesis depending on the python version... and the code to fix the new versions, fails in the old versions.
If we use the newest hypothesis on each python version, the code will fail on some and run on others. To ensure it runs on all, we need to pin hypothesis instead to an old enough version of the lib :(
This fixes two issues that were prevent pipelines from running:
Regarding the old version of hypothesis:
The newer versions require adding a specific health check to a skip list, otherwise many tests fail. But those hypothesis versions don't run on python 3.4, so the pipelines end up using an older hypothesis depending on the python version... and the code to fix the new versions, fails in the old versions. If we use the newest hypothesis on each python version, the code will fail on some and run on others. To ensure it runs on all, we need to pin hypothesis instead to an old enough version of the lib :(