Respect auto_download even if IERS_Auto predictive values are stale

astropy/utils/iers/iers.py

@@ -905,6 +905,16 @@ def _refresh_table_as_needed(self, mjd):
         if max_input_mjd > predictive_mjd and (now_mjd - predictive_mjd) > auto_max_age:
             all_urls = (conf.iers_auto_url, conf.iers_auto_url_mirror)
 
+            # Bail out with a warning if downloading is disabled
+            if not conf.auto_download:
+                warn(
+                    IERSStaleWarning(
+                        "IERS_Auto predictive values are older than"
+                        f" {conf.auto_max_age} days but downloading is disabled"
+                    )
+                )
+                return
+
             # Get the latest version
             try:
                 filename = download_file(all_urls[0], sources=all_urls, cache="update")

astropy/utils/iers/tests/test_iers.py

@@ -341,12 +341,18 @@ def test_simple(self):
                 dat.ut1_utc(Time(60000, format="mjd").jd)
             assert len(warns) == 1
 
-            # Warning only if we are getting return status
+            # Warning only (i.e., no exception) if we are getting return status
             with pytest.warns(
-                iers.IERSStaleWarning, match="IERS_Auto predictive values are older"
-            ) as warns:
+                iers.IERSStaleWarning, match="IERS_Auto predictive values are older.*did not find newer values"
+            ):
                 dat.ut1_utc(Time(60000, format="mjd").jd, return_status=True)
-            assert len(warns) == 1
+
+            # Confirm that the warning message is different if downloading is disabled
+            with pytest.warns(
+                iers.IERSStaleWarning, match=r"IERS_Auto predictive values are older.*downloading is disabled"
+            ):
+                with iers.conf.set_temp("auto_download", False):
+                    dat.ut1_utc(Time(60000, format="mjd").jd, return_status=True)
 
             # Now set auto_max_age = None which says that we don't care how old the
             # available IERS-A file is.  There should be no warnings or exceptions.