Handle renderer process not starting at all

qutebrowser/browser/browsertab.py

@@ -78,7 +78,8 @@ TerminationStatus = usertypes.enum('TerminationStatus', [
     'normal',
     'abnormal',  # non-zero exit status
     'crashed',   # e.g. segfault
-    'killed'
+    'killed',
+    'unknown',
 ])
 
 

qutebrowser/browser/webengine/webenginetab.py

@@ -693,6 +693,8 @@ class WebEngineTab(browsertab.AbstractTab):
                 browsertab.TerminationStatus.crashed,
             QWebEnginePage.KilledTerminationStatus:
                 browsertab.TerminationStatus.killed,
+            -1:
+                browsertab.TerminationStatus.unknown,
         }
         self.renderer_process_terminated.emit(status_map[status], exitcode)
 

qutebrowser/mainwindow/tabbedbrowser.py

@@ -677,6 +677,8 @@ class TabbedBrowser(tabwidget.TabWidget):
             message.error("Renderer process crashed")
         elif status == browsertab.TerminationStatus.killed:
             message.error("Renderer process was killed")
+        elif status == browsertab.TerminationStatus.unknown:
+            message.error("Renderer process did not start")
         else:
             raise ValueError("Invalid status {}".format(status))