Set TMPDIR to RUNNER_TEMP on CI

The upload artifact action can't collect artifacts from /tmp/ in the test
runners. So now that we are writing the screenshots that we want to collect
later to the pytest `tmp_path` location we need to make sure that lives
somewhere the later actions can find it.

Pytest uses `tempfile.gettempdir()` to find the temp dir, and that respects a
number of environment variables including `TMPDIR`. This commits sets TMPDIR
to RUNNER_TEMP in in our test runners to make pytest uses the temp dir that's
mounted into the action containers.

For the docker based runners I can use the `env` map, but for the ubuntu ones
it didn't let me expand `${{ runner.temp }}` in the end map under `step`, so
I'm writing it to the env file for the runner instead. It failed to parse the
action yaml and said:

    > Unrecognized named-value: 'runner'. Located at position 1 within expression: runner.temp

For the user part of the `pytest-of-$user` directory, I looked at the new
screenshot related test summary lines to see what the user was called.
`runner` on the ubuntu containers and `user` in our docker containers. Pytest
maintains the "pytest-current" symlink to the latest temp folder.

.github/workflows/bleeding.yml

@@ -27,6 +27,7 @@ jobs:
         PY_COLORS: "1"
         DOCKER: "${{ matrix.image }}"
         CI: true
+        TMPDIR: "${{ runner.temp }}"
       volumes:
         # Hardcoded because we can't use ${{ runner.temp }} here apparently.
         - /home/runner/work/_temp/:/home/runner/work/_temp/
@@ -54,7 +55,7 @@ jobs:
         with:
           name: "end2end-screenshots-${{ steps.info.outputs.date }}-${{ steps.info.outputs.sha_short }}-${{ matrix.image }}"
           path: |
-            ${{ runner.temp }}/pytest-screenshots/*.png
+            ${{ runner.temp }}/pytest-of-user/pytest-current/pytest-screenshots/*.png
           if-no-files-found: ignore
         if: failure()
   irc:

.github/workflows/ci.yml

@@ -107,6 +107,7 @@ jobs:
         DOCKER: "${{ matrix.image }}"
         CI: true
         PYTEST_ADDOPTS: "--color=yes"
+        TMPDIR: "${{ runner.temp }}"
       volumes:
         # Hardcoded because we can't use ${{ runner.temp }} here apparently.
         - /home/runner/work/_temp/:/home/runner/work/_temp/
@@ -131,7 +132,7 @@ jobs:
         with:
           name: "end2end-screenshots-${{ steps.info.outputs.date }}-${{ steps.info.outputs.sha_short }}-${{ matrix.image }}"
           path: |
-            ${{ runner.temp }}/pytest-screenshots/*.png
+            ${{ runner.temp }}/pytest-of-user/pytest-current/pytest-screenshots/*.png
           if-no-files-found: ignore
         if: failure()
 
@@ -237,6 +238,8 @@ jobs:
       - name: Upgrade 3rd party assets
         run: "tox exec -e ${{ matrix.testenv }} -- python scripts/dev/update_3rdparty.py --gh-token ${{ secrets.GITHUB_TOKEN }}"
         if: "startsWith(matrix.os, 'windows-')"
+      - name: "Set TMPDIR for pytest"
+        run: 'echo "TMPDIR=${{ runner.temp }}" >> "$GITHUB_ENV"'
       - name: "Run ${{ matrix.testenv }}"
         run: "dbus-run-session -- tox -e ${{ matrix.testenv }} -- ${{ matrix.args }}"
         if: "startsWith(matrix.os, 'ubuntu-')"
@@ -263,7 +266,7 @@ jobs:
         with:
           name: "end2end-screenshots-${{ steps.info.outputs.date }}-${{ steps.info.outputs.sha_short }}-${{ matrix.testenv }}-${{ matrix.os }}"
           path: |
-            ${{ runner.temp }}/pytest-screenshots/*.png
+            ${{ runner.temp }}/pytest-of-runner/pytest-current/pytest-screenshots/*.png
           if-no-files-found: ignore
         if: failure()