Drop old Debian error page workaround

Manual revert of d741bdf

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882805

See qutebrowser#5078, qutebrowser#3773

doc/changelog.asciidoc

@@ -72,6 +72,9 @@ Fixed
   with `confirm_quit` and multiple windows remain.
 - Crash when a previous crash-log file contains non-ASCII characters (which
   should never happen unless it was edited manually)
+- Due to changes in Debian, an old workaround (for broken QtWebEngine patching
+  on Debian) caused the inferior qutebrowser error page to be displayed, when
+  Chromium's would have worked fine. The workaround was now dropped.
 
 [[v2.4.1]]
 v2.4.1 (unreleased)

qutebrowser/browser/webengine/webenginetab.py

@@ -1522,27 +1522,21 @@ def _on_render_process_terminated(self, status, exitcode):
         }
         self.renderer_process_terminated.emit(status_map[status], exitcode)
 
-    def _error_page_workaround(self, js_enabled, html):
+    def _error_page_workaround(self, html):
         """Check if we're displaying a Chromium error page.
 
-        This gets called if we got a loadFinished(False), so we can display at
-        least some error page in situations where Chromium's can't be
+        This gets called if we got a loadFinished(False) without JavaScript, so
+        we can display at least some error page, since Chromium's can't be
         displayed.
 
         WORKAROUND for https://bugreports.qt.io/browse/QTBUG-66643
-        WORKAROUND for https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882805
         """
         match = re.search(r'"errorCode":"([^"]*)"', html)
         if match is None:
             return
 
         error = match.group(1)
         log.webview.error("Load error: {}".format(error))
-
-        missing_jst = 'jstProcess(' in html and 'jstProcess=' not in html
-        if js_enabled and not missing_jst:
-            return
-
         self._show_error_page(self.url(), error=error)
 
     @pyqtSlot(int)
@@ -1565,9 +1559,8 @@ def _on_load_finished(self, ok: bool) -> None:
             # WORKAROUND for https://bugreports.qt.io/browse/QTBUG-65223
             self._update_load_status(ok)
 
-            self.dump_async(functools.partial(
-                self._error_page_workaround,
-                self.settings.test_attribute('content.javascript.enabled')))
+            if not self.settings.test_attribute('content.javascript.enabled'):
+                self.dump_async(self._error_page_workaround)
 
     @pyqtSlot(certificateerror.CertificateErrorWrapper)
     def _on_ssl_errors(self, error):