Revert "Never delete crash log file."

This reverts commit dcad41c92e.

Shutdown segfaults still happen too often, and the crash log doesn't tell us
anything useful...

qutebrowser/app.py

@@ -416,6 +416,23 @@ class Application(QApplication):
                 pass
             state_config['geometry']['mainwindow'] = geom
 
+    def _destroy_crashlogfile(self):
+        """Clean up the crash log file and delete it."""
+        if self._crashlogfile is None:
+            return
+        # We use sys.__stderr__ instead of sys.stderr here so this will still
+        # work when sys.stderr got replaced, e.g. by "Python Tools for Visual
+        # Studio".
+        if sys.__stderr__ is not None:
+            faulthandler.enable(sys.__stderr__)
+        else:
+            faulthandler.disable()
+        self._crashlogfile.close()
+        try:
+            os.remove(self._crashlogfile.name)
+        except (PermissionError, FileNotFoundError):
+            log.destroy.exception("Could not remove crash log!")
+
     def _exception_hook(self, exctype, excvalue, tb):
         """Handle uncaught python exceptions.
 
@@ -476,6 +493,7 @@ class Application(QApplication):
         # run in some undefined state, so we only do the most needed shutdown
         # here.
         qInstallMessageHandler(None)
+        self._destroy_crashlogfile()
         sys.exit(1)
 
     @cmdutils.register(instance='app', name=['quit', 'q'])
@@ -694,6 +712,9 @@ class Application(QApplication):
                 except AttributeError as e:
                     log.destroy.warning("Could not save {}.".format(what))
                     log.destroy.debug(e)
+        # Re-enable faulthandler to stdout, then remove crash log
+        log.destroy.debug("Deactiving crash log...")
+        self._destroy_crashlogfile()
         # If we don't kill our custom handler here we might get segfaults
         log.destroy.debug("Deactiving message handler...")
         qInstallMessageHandler(None)