Fix pytest command not found in CI by using python3 -m pytest

Author: tomchapman

tests/run_integrated_tests.sh

@@ -7,5 +7,5 @@ export PYTHONPATH="@PROJECT_BINARY_DIR@/tools/pylib:@PROJECT_SOURCE_DIR@/tools/p
 # Pre-build the project to prevent concurrent CMake race conditions
 cmake --build "$PROJECT_ROOT"
 
-pytest -m "not serial" --cache-clear -n auto --dist=loadgroup -q "$PROJECT_ROOT/tests/integrated" "$@"
-pytest -m serial "$PROJECT_ROOT/tests/integrated" "$@"
+python3 -m pytest -m "not serial" --cache-clear -n auto --dist=loadgroup -q "$PROJECT_ROOT/tests/integrated" "$@"
+python3 -m pytest -m serial "$PROJECT_ROOT/tests/integrated" "$@"