Revert "chore: revert check where airmass skips on python 3.9 (#1708)"

This reverts commit b56c2af.

Author: schloerke

tests/playwright/examples/test_examples.py

@@ -12,6 +12,7 @@
 def test_examples(page: Page, ex_app_path: str) -> None:
 
     skip_on_windows_with_timezonefinder(ex_app_path)
+    skip_airmass_on_3_9(ex_app_path)
 
     validate_example(page, ex_app_path)
 
@@ -33,3 +34,33 @@ def skip_on_windows_with_timezonefinder(ex_app_path: str) -> None:
         pytest.skip(
             "timezonefinder has difficulty compiling on windows. Skipping example app. posit-dev/py-shiny#1651"
         )
+
+
+def skip_airmass_on_3_9(ex_app_path: str) -> None:
+    print(ex_app_path)
+    if ex_app_path != "examples/airmass/app.py":
+        return
+
+    import sys
+
+    if sys.version_info[:2] != (3, 9):
+        return
+
+    try:
+        # Astropy loads `numpy` at run time
+        import astropy.coordinates as _  # pyright: ignore # noqa: F401
+        import astropy.units as __  # pyright: ignore # noqa: F401
+
+        # Future proofing: if astropy is _actually_ loading, raise an error
+        raise RuntimeError(
+            "This code believes astropy and numpy have difficulty loading on python 3.9. Please remove this check if it is no longer true."
+        )
+    except AttributeError as e:
+        if "numpy" in str(e) and "product" in str(e):
+            pytest.skip(
+                "astropy and numpy has difficulty loading on python 3.9. Skipping example app: airmass. posit-dev/py-shiny#1678"
+            )
+            return
+
+        # Future proofing: if the error is not what we expect, raise it
+        raise e