Improve parsing of invalid keys

This should handle "<>" and "\x1f" correctly.

qutebrowser/keyinput/keyutils.py

@@ -413,12 +413,12 @@ class KeySequence:
 
     def _validate(self, keystr=None):
         for info in self:
-            assert Qt.Key_Space <= info.key <= Qt.Key_unknown, info.key
-            if info.key == Qt.Key_unknown:
-                raise KeyParseError(keystr, "Got unknown key!")
+            if info.key < Qt.Key_Space or info.key >= Qt.Key_unknown:
+                raise KeyParseError(keystr, "Got invalid key!")
 
         for seq in self._sequences:
-            assert seq
+            if not seq:
+                raise KeyParseError(keystr, "Got invalid key!")
 
     def matches(self, other):
         """Check whether the given KeySequence matches with this one.

tests/unit/keyinput/test_keyutils.py

@@ -19,6 +19,8 @@
 
 import operator
 
+import hypothesis
+from hypothesis import strategies
 import pytest
 from PyQt5.QtCore import Qt, QEvent, pyqtSignal
 from PyQt5.QtGui import QKeyEvent, QKeySequence
@@ -203,15 +205,11 @@ class TestKeySequence:
         seq = keyutils.KeySequence()
         assert not seq
 
-    @pytest.mark.parametrize('key', [Qt.Key_unknown, -1])
+    @pytest.mark.parametrize('key', [Qt.Key_unknown, -1, '\x1f', 0])
     def test_init_unknown(self, key):
         with pytest.raises(keyutils.KeyParseError):
             keyutils.KeySequence(key)
 
-    def test_init_invalid(self):
-        with pytest.raises(AssertionError):
-            keyutils.KeySequence(0)
-
     @pytest.mark.parametrize('orig, normalized', [
         ('<Control+x>', '<Ctrl+x>'),
         ('<Windows+x>', '<Meta+x>'),
@@ -410,6 +408,7 @@ class TestKeySequence:
         ('<alt+<>', keyutils.KeyParseError),
         ('<alt+>>', keyutils.KeyParseError),
         ('<blub>', keyutils.KeyParseError),
+        ('<>', keyutils.KeyParseError),
         ('\U00010000', keyutils.KeyParseError),
     ])
     def test_parse(self, keystr, expected):
@@ -419,6 +418,15 @@ class TestKeySequence:
         else:
             assert keyutils.KeySequence.parse(keystr) == expected
 
+    @hypothesis.given(strategies.text())
+    def test_parse_hypothesis(self, keystr):
+        try:
+            seq = keyutils.KeySequence.parse(keystr)
+        except keyutils.KeyParseError:
+            pass
+        else:
+            str(seq)
+
 
 def test_key_info_from_event():
     ev = QKeyEvent(QEvent.KeyPress, Qt.Key_A, Qt.ShiftModifier, 'A')