Enable tracebacks when running mypy (#3425)

This will make it easier to diagnose intermittent mypy crashes

Author: correctmost

.github/workflows/mypy.yaml

@@ -20,4 +20,4 @@ jobs:
             - run: python --version
             - run: mypy --version
             - name: run mypy
-              run: mypy --config-file pyproject.toml
+              run: mypy --show-traceback --config-file pyproject.toml

.pre-commit-config.yaml

@@ -39,6 +39,7 @@ repos:
     hooks:
     - id: mypy
       args: [
+        '--show-traceback',
         '--config-file=pyproject.toml'
       ]
       fail_fast: true