TimelineWebView: Log WebKit import fail reason (#3883)

If we only raise an exception from the WebEngine import failure,
then we lose any visibility into the reason WHY the WebKit backend
failed to load. (Important if the failure reason is a code error,
not a missing PyQtWebKit module.)

Author: ferdnyc

src/windows/views/webview.py

@@ -169,7 +169,7 @@
             from .webview_backend.webkit import TimelineWebKitView as WebViewClass
             WEBVIEW_LOADED = True
         except ImportError:
-            pass
+            log.error("Import failure loading WebKit backend", exc_info=1)
         finally:
             if not WEBVIEW_LOADED:
                 raise RuntimeError(