[build,scripts,data] Rename nosetests specific mark expression to be more generic and enable pytest equivalent

This is like nightlies with resume.
You can avoid rebuilding all packages.

The latest version does currently not install
all its depdencies.

This reverts commit 0012b6ed.

[conda] Update packaging pin following release of version 19.2 on conda channel (https://github.com/ContinuumIO/anaconda-issues/issues/11236)