flow: guard test files against missing pytest in CI

CI runs `python "$file"` on every .py in flow/test/.
conftest.py and test_platform_config.py import pytest which
isn't installed in the testUtilScripts CI environment.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

Author: oharboe

flow/test/conftest.py

@@ -1,7 +1,10 @@
-import pytest
+try:
+    import pytest
+except ImportError:
+    pass
+else:
 
-
-def pytest_configure(config):
-    config.addinivalue_line(
-        "markers", "integration: mark test as integration test (requires Make)"
-    )
+    def pytest_configure(config):
+        config.addinivalue_line(
+            "markers", "integration: mark test as integration test (requires Make)"
+        )

flow/test/test_platform_config.py

@@ -1195,4 +1195,10 @@ def test_make_metadata(self, platform, design):
 
 
 if __name__ == "__main__":
-    pytest.main([__file__, "-v", "-m", "not integration"])
+    try:
+        import pytest
+
+        pytest.main([__file__, "-v", "-m", "not integration"])
+    except ImportError:
+        print("pytest not installed, skipping tests")
+        pass