Handle more test flakiness

tests/end2end/features/backforward.feature

@@ -3,7 +3,7 @@
 Feature: Going back and forward.
     Testing the :back/:forward commands.
 
-    @flaky
+    @skip  # Too flaky
     Scenario: Going back/forward
         Given I open data/backforward/1.txt
         When I open data/backforward/2.txt

tests/end2end/features/editor.feature

@@ -86,6 +86,7 @@ Feature: Opening external editors
         When I run :edit-url -t -b
         Then the error "Only one of -t/-b/-w can be given!" should be shown
 
+    @flaky
     Scenario: Editing a URL with invalid URL
         When I set url.auto_search to never
         And I open data/hello.txt

tests/end2end/features/misc.feature

@@ -533,14 +533,14 @@ Feature: Various utility commands.
         Then "Renderer process crashed" should be logged
         And "* 'Error loading chrome://crash/'" should be logged
 
-    @qtwebkit_skip @no_invalid_lines @qt>=5.9
+    @qtwebkit_skip @no_invalid_lines @qt>=5.9 @flaky
     Scenario: Renderer kill (5.9)
         When I run :open -t chrome://kill
         Then "Renderer process was killed" should be logged
         And "* 'Error loading chrome://kill/'" should be logged
 
     # https://github.com/qutebrowser/qutebrowser/issues/2290
-    @qtwebkit_skip @no_invalid_lines
+    @qtwebkit_skip @no_invalid_lines @flaky
     Scenario: Navigating to URL after renderer process is gone
         When I run :tab-only
         And I open data/numbers/1.txt

tests/end2end/features/sessions.feature

@@ -228,7 +228,7 @@ Feature: Saving and loading sessions
             url: http://localhost:*/data/hello.txt
 
   # Seems like that bug is fixed upstream in QtWebEngine
-  @qtwebkit_skip
+  @qtwebkit_skip @flaky
   Scenario: Saving a session with a page using history.replaceState() and navigating away
     When I open data/sessions/history_replace_state.html without waiting
     And I wait for "* Called history.replaceState" in the log
@@ -363,7 +363,7 @@ Feature: Saving and loading sessions
     And I replace "about:blank" by "http://localhost:(port)/data/numbers/2.txt" in the "loaded_session" session file
     And I run :session-load loaded_session
     Then data/numbers/2.txt should be loaded
-  
+
   @qtwebengine_flaky
   Scenario: Loading and deleting a session
     When I open about:blank

tests/end2end/test_hints_html.py

@@ -117,7 +117,7 @@ def test_hints(test_name, zoom_text_only, zoom_level, find_implementation,
         quteproc.set_setting('hints.find_implementation', 'javascript')
 
 
-@pytest.mark.flaky
+@pytest.mark.skip  # Too flaky
 def test_word_hints_issue1393(quteproc, tmpdir):
     dict_file = tmpdir / 'dict'
     dict_file.write(textwrap.dedent("""