tests/: move install of mypy to tests/conftest.py.

Simplifies disabling of use of `pip install`, e.g. with system builds.

Author: julian-smith-artifex-com

tests/conftest.py

@@ -19,7 +19,7 @@ def install_required_packages():
         # We can't run child processes, so rely on required test packages
         # already being installed, e.g. in our wheel's <requires_dist>.
         return
-    packages = 'pytest fontTools pymupdf-fonts flake8 pylint codespell'
+    packages = 'pytest fontTools pymupdf-fonts flake8 pylint codespell mypy'
     if platform.system() == 'Windows' and int.bit_length(sys.maxsize+1) == 32:
         # No pillow wheel available, and doesn't build easily.
         pass

tests/test_typing.py

@@ -20,8 +20,6 @@ def test_py_typed():
         return
 
     print(f'test_py_typed(): {pymupdf.__path__=}')
-    run('pip uninstall -y mypy')
-    run('pip install mypy')
     root = os.path.abspath(f'{__file__}/../..')
 
     # Run mypy on this .py file; it will fail at `import pymypdf` if the