tests/functional: retry when seeing ConnectionError exception

This base class is used for many different socket connection
errors, corresponding to ECONNRESET, ECONNREFUSED, ECONNABORTED
and more. Most of these are things you might expect to see every
now and then as transient flaws. We should thus retry the asset
download when seeing them.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250918125746.1165658-2-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/functional/qemu_test/asset.py

@@ -179,6 +179,13 @@ class Asset:
                                self.url, e.reason)
                 raise AssetError(self, "Unable to download: URL error %s" %
                                  e.reason, transient=True)
+            except ConnectionError as e:
+                # A socket connection failure, such as dropped conn
+                # or refused conn
+                tmp_cache_file.unlink()
+                self.log.error("Unable to download %s: Connection error %s",
+                               self.url, e)
+                continue
             except Exception as e:
                 tmp_cache_file.unlink()
                 raise AssetError(self, "Unable to download: %s" % e)