Make ophaned editor test less flaky.

Instead of having the editor sleep a short time, explicitly send it a
signal to exit.

tests/end2end/features/editor.feature

@@ -116,14 +116,15 @@ Feature: Opening external editors
         Then the javascript message "text: foobar" should be logged
 
     Scenario: Spawning an editor and closing the tab
-        When I set up a fake editor returning "foo" after 1s
+        When I set up a fake editor that waits
         And I open data/editor.html
         And I run :click-element id qute-textarea
         And I wait for "Entering mode KeyMode.insert (reason: clicking input)" in the log
         And I run :open-editor
         And I set tabs.last_close to blank
         And I run :tab-close
-        Then the warning "Edited element was closed" should be shown
+        And I kill the waiting editor
+        Then the warning "Edited element vanished" should be shown
 
     @qtwebengine_todo: Caret mode is not implemented yet
     Scenario: Spawning an editor in caret mode

tests/end2end/features/test_editor_bdd.py

@@ -20,6 +20,8 @@
 import sys
 import json
 import textwrap
+import os
+import signal
 
 import pytest_bdd as bdd
 bdd.scenarios('editor.feature')
@@ -66,19 +68,31 @@ def set_up_editor_empty(quteproc, server, tmpdir):
     set_up_editor(quteproc, server, tmpdir, "")
 
 
-@bdd.when(bdd.parsers.parse(
-    'I set up a fake editor returning "{text}" after {t}s'))
-def set_up_editor_delay(quteproc, server, tmpdir, text, t):
+@bdd.when(bdd.parsers.parse('I set up a fake editor that waits'))
+def set_up_editor_wait(quteproc, server, tmpdir):
     """Set up editor.command to a small python script inserting a text."""
+    pidfile = tmpdir / 'editor_pid'
     script = tmpdir / 'script.py'
     script.write(textwrap.dedent("""
+        import os
         import sys
         import time
+        import signal
 
-        time.sleep({t})
+        with open('{pidfile}', 'w') as f:
+            f.write(str(os.getpid()))
 
-        with open(sys.argv[1], 'w', encoding='utf-8') as f:
-            f.write({text!r})
-    """.format(text=text, t=t)))
+        signal.signal(signal.SIGUSR1, lambda s, f: sys.exit(0))
+
+        time.sleep(100)
+    """.format(pidfile=pidfile)))
     editor = json.dumps([sys.executable, str(script), '{}'])
     quteproc.set_setting('editor.command', editor)
+
+
+@bdd.when(bdd.parsers.parse('I kill the waiting editor'))
+def kill_editor_wait(quteproc, server, tmpdir):
+    """Kill the waiting editor."""
+    pidfile = tmpdir / 'editor_pid'
+    pid = int(pidfile.read())
+    os.kill(pid, signal.SIGUSR1)