use a temporary attribute of the class to prevent the loop; tested to work in both backends

qutebrowser/browser/browsertab.py

@@ -99,7 +99,6 @@ class TabData:
                          Only used for QtWebKit.
         pinned: Flag to pin the tab.
         fullscreen: Whether the tab has a video shown fullscreen currently.
-        netrc_used: flag to avoid endless loop when using netrc
     """
 
     keep_icon = attr.ib(False)
@@ -108,7 +107,6 @@ class TabData:
     override_target = attr.ib(None)
     pinned = attr.ib(False)
     fullscreen = attr.ib(False)
-    netrc_used = False
 
 
 class AbstractAction:
@@ -726,7 +724,12 @@ class AbstractTab(QWidget):
         self._progress = 0
         self._has_ssl_errors = False
         self.data.viewing_source = False
-        self.data.netrc_used = False
+        if self.backend == usertypes.Backend.QtWebKit:
+            obj = self.networkaccessmanager()
+        else:
+            obj = self
+        if hasattr(obj, 'netrc_used'):
+            delattr(obj, 'netrc_used')
         self._set_load_status(usertypes.LoadStatus.loading)
         self.load_started.emit()
 

qutebrowser/browser/webengine/webenginetab.py

@@ -19,7 +19,6 @@
 
 """Wrapper over a QWebEngineView."""
 
-import os
 import math
 import functools
 import html as html_utils
@@ -741,8 +740,8 @@ class WebEngineTab(browsertab.AbstractTab):
     @pyqtSlot(QUrl, 'QAuthenticator*')
     def _on_authentication_required(self, url, authenticator):
         netrc = None
-        if not self.data.netrc_used:
-            self.data.netrc_used = True
+        if not hasattr(self, 'netrc_used'):
+            setattr(self, 'netrc_used', True)
             netrc = shared.netrc_authentication(url, authenticator)
         if not netrc:
             abort_on = [self.shutting_down, self.load_started]

qutebrowser/browser/webkit/network/networkmanager.py

@@ -269,8 +269,8 @@ class NetworkManager(QNetworkAccessManager):
     def on_authentication_required(self, reply, authenticator):
         """Called when a website needs authentication."""
         netrc = False
-        if not self.data.netrc_used:
-            self.data.netrc_used = True
+        if not hasattr(self, 'netrc_used'):
+            setattr(self, 'netrc_used', True)
             netrc = shared.netrc_authentication(reply.url(), authenticator)
         if not netrc:
             abort_on = self._get_abort_signals(reply)