Add missing configexc.py file.

I forgot to add this in 512d7c4448b0610bc133d83d8280a94469841968...

qutebrowser/config/configexc.py

@@ -0,0 +1,77 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2014 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/>.
+
+"""Exceptions related to config parsing."""
+
+
+class Error(Exception):
+
+    """Base exception for config-related errors."""
+
+    pass
+
+
+class ValidationError(Error):
+
+    """Raised when a value for a config type was invalid.
+
+    Attributes:
+        section: Section in which the error occured (added when catching and
+                 re-raising the exception).
+        option: Option in which the error occured.
+    """
+
+    def __init__(self, value, msg):
+        super().__init__("Invalid value '{}' - {}".format(value, msg))
+        self.section = None
+        self.option = None
+
+
+class NoSectionError(Error):
+
+    """Raised when no section matches a requested option."""
+
+    def __init__(self, section):
+        super().__init__("Section {!r} does not exist!".format(section))
+        self.section = section
+
+
+class NoOptionError(Error):
+
+    """Raised when an option was not found."""
+
+    def __init__(self, option, section):
+        super().__init__("No option {!r} in section: {!r}".format(
+            option, section))
+        self.option = option
+        self.section = section
+
+
+class InterpolationSyntaxError(Error):
+
+    """Raised when the source text contains invalid syntax.
+
+    Current implementation raises this exception when the source text into
+    which substitutions are made does not conform to the required syntax.
+    """
+
+    def __init__(self, option, section, msg):
+        super().__init__(msg)
+        self.option = option
+        self.section = section