Fix starting when sys.stderr is None

CHANGELOG.asciidoc

@@ -66,6 +66,7 @@ Fixed
 - Fixed updating the tab index in the statusbar when opening a background tab
 - Fixed a crash when entering `:-- ` in the commandline
 - Fixed `:debug-console` with PyQt 5.6
+- Fixed qutebrowser not starting when `sys.stderr` is `None`
 
 v0.6.2
 ------

qutebrowser/misc/earlyinit.py

@@ -123,7 +123,8 @@ def init_faulthandler(fileobj=sys.__stderr__):
         # start.
         return
     faulthandler.enable(fileobj)
-    if hasattr(faulthandler, 'register') and hasattr(signal, 'SIGUSR1'):
+    if (hasattr(faulthandler, 'register') and hasattr(signal, 'SIGUSR1') and
+            sys.stderr is not None):
         # If available, we also want a traceback on SIGUSR1.
         # pylint: disable=no-member,useless-suppression
         faulthandler.register(signal.SIGUSR1)

tests/unit/misc/test_earlyinit.py

@@ -0,0 +1,33 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2016 Florian Bruhin (The-Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Test qutebrowser.misc.earlyinit."""
+
+import sys
+
+import pytest
+
+from qutebrowser.misc import earlyinit
+
+
+@pytest.mark.parametrize('attr', ['stderr', '__stderr__'])
+def test_init_faulthandler_stderr_none(monkeypatch, attr):
+    """Make sure init_faulthandler works when sys.stderr/__stderr__ is None."""
+    monkeypatch.setattr(sys, attr, None)
+    earlyinit.init_faulthandler()