diff --git a/data/coverage.svg b/data/coverage.svg
index 4b105c68..5b40c8fe 100644
--- a/data/coverage.svg
+++ b/data/coverage.svg
@@ -15,7 +15,7 @@
     <g fill="#fff" text-anchor="middle" font-family="DejaVu Sans,Verdana,Geneva,sans-serif" font-size="11">
         <text x="31.5" y="15" fill="#010101" fill-opacity=".3">coverage</text>
         <text x="31.5" y="14">coverage</text>
-        <text x="80" y="15" fill="#010101" fill-opacity=".3">82%</text>
-        <text x="80" y="14">82%</text>
+        <text x="80" y="15" fill="#010101" fill-opacity=".3">83%</text>
+        <text x="80" y="14">83%</text>
     </g>
 </svg>
diff --git a/data/pylint.svg b/data/pylint.svg
index 280836f4..df8fd8a5 100644
--- a/data/pylint.svg
+++ b/data/pylint.svg
@@ -17,7 +17,7 @@
         <text x="22.0" y="14">pylint</text>
     </g>
     <g fill="#fff" text-anchor="middle" font-family="DejaVu Sans,Verdana,Geneva,sans-serif" font-size="11">
-        <text x="63.0" y="15" fill="#010101" fill-opacity=".3">9.66</text>
-        <text x="62.0" y="14">9.66</text>
+        <text x="63.0" y="15" fill="#010101" fill-opacity=".3">9.82</text>
+        <text x="62.0" y="14">9.82</text>
     </g>
 </svg>
\ No newline at end of file
diff --git a/keymapper/daemon.py b/keymapper/daemon.py
index e3a193aa..a637ae49 100644
--- a/keymapper/daemon.py
+++ b/keymapper/daemon.py
@@ -24,6 +24,7 @@
 
 import subprocess
 
+import dbus
 from dbus import service
 import dbus.mainloop.glib
 
@@ -57,7 +58,7 @@ def get_dbus_interface():
         remote_object = bus.get_object('keymapper.Control', '/')
         interface = dbus.Interface(remote_object, 'keymapper.Interface')
         logger.debug('Connected to dbus')
-    except Exception as error:
+    except dbus.exceptions.DBusException as error:
         logger.error(
             'Could not connect to the dbus of "key-mapper-service", mapping '
             'keys only works as long as the window is open.'
@@ -86,7 +87,11 @@ class Daemon(service.Object):
                 print(device, preset)
                 mapping = Mapping()
                 mapping.load(device, preset)
-                self.injectors[device] = KeycodeInjector(device, mapping)
+                try:
+                    injector = KeycodeInjector(device, mapping)
+                    self.injectors[device] = injector
+                except OSError as error:
+                    logger.error(error)
         super().__init__(*args, **kwargs)
 
     @dbus.service.method(
diff --git a/keymapper/dev/permissions.py b/keymapper/dev/permissions.py
index b8c923c5..1dc65a74 100644
--- a/keymapper/dev/permissions.py
+++ b/keymapper/dev/permissions.py
@@ -40,8 +40,10 @@ def can_read_devices():
     def warn(group):
         logger.warning(
             'Some devices may not be visible without being in the '
-            f'"{group}" user group. Try `sudo usermod -a -G {group} $USER` '
-            'and log out and back in.'
+            f'"%s" user group. Try `sudo usermod -a -G %s $USER` '
+            'and log out and back in.',
+            group,
+            group
         )
 
     if not is_root and not is_test:
diff --git a/keymapper/gtk/row.py b/keymapper/gtk/row.py
index 5aa382d6..4e453d7a 100644
--- a/keymapper/gtk/row.py
+++ b/keymapper/gtk/row.py
@@ -109,6 +109,7 @@ class Row(Gtk.ListBoxRow):
         self.get_style_context().remove_class('changed')
 
     def on_character_input_change(self, _):
+        """When the output character for that keycode is typed in."""
         keycode = self.get_keycode()
         character = self.get_character()
 
diff --git a/keymapper/logger.py b/keymapper/logger.py
index 32fd4afe..5cc8950c 100644
--- a/keymapper/logger.py
+++ b/keymapper/logger.py
@@ -27,13 +27,17 @@ import logging
 import pkg_resources
 
 
+SPAM = 5
+
+
 def spam(self, message, *args, **kws):
+    """Log a more-verbose message than debug."""
+    # pylint: disable=protected-access
     if self.isEnabledFor(SPAM):
         # https://stackoverflow.com/a/13638084
         self._log(SPAM, message, args, **kws)
 
 
-SPAM = 5
 logging.addLevelName(SPAM, "SPAM")
 logging.Logger.spam = spam
 
@@ -42,10 +46,11 @@ class Formatter(logging.Formatter):
     """Overwritten Formatter to print nicer logs."""
     def format(self, record):
         """Overwritten format function."""
+        # pylint: disable=protected-access
         debug = logger.level <= logging.DEBUG
         if record.levelno == logging.INFO and not debug:
             # if not launched with --debug, then don't print "INFO:"
-            self._style._fmt = '%(message)s'  # pylint: disable=line-too-long
+            self._style._fmt = '%(message)s'
         else:
             # see https://en.wikipedia.org/wiki/ANSI_escape_code#3/4_bit
             # for those numbers
diff --git a/keymapper/mapping.py b/keymapper/mapping.py
index 3ae5715a..89750bd8 100644
--- a/keymapper/mapping.py
+++ b/keymapper/mapping.py
@@ -30,19 +30,11 @@ from keymapper.logger import logger
 from keymapper.paths import get_config_path
 
 
-def update_reverse_mapping(func):
-    """Generate a reverse mapping to optimize reverse lookups.
-
-    If _mapping contains `20: "a, A"` (the xkb syntax for modified keys),
-    reverse mapping will contain `"a": 20, "A": 20`.
-    """
+def keep_reverse_mapping_intact(func):
+    """Decorator for Mapping.update_reverse_mapping."""
     def wrapper(self, *args, **kwargs):
         func(self, *args, **kwargs)
-
-        self._reverse_mapping = {}
-        for key, value in self._mapping.items():
-            for character in value.split(','):
-                self._reverse_mapping[character.strip()] = key
+        self.update_reverse_mapping()
     return wrapper
 
 
@@ -71,7 +63,18 @@ class Mapping:
     def __len__(self):
         return len(self._mapping)
 
-    @update_reverse_mapping
+    def update_reverse_mapping(self):
+        """Generate a reverse mapping to optimize reverse lookups.
+
+        If _mapping contains `20: "a, A"` (the xkb syntax for modified keys),
+        reverse mapping will contain `"a": 20, "A": 20`.
+        """
+        self._reverse_mapping = {}
+        for key, value in self._mapping.items():
+            for character in value.split(','):
+                self._reverse_mapping[character.strip()] = key
+
+    @keep_reverse_mapping_intact
     def change(self, new_keycode, character, previous_keycode=None):
         """Replace the mapping of a keycode with a different one.
 
@@ -110,7 +113,7 @@ class Mapping:
 
         return False
 
-    @update_reverse_mapping
+    @keep_reverse_mapping_intact
     def clear(self, keycode):
         """Remove a keycode from the mapping.
 
@@ -122,13 +125,13 @@ class Mapping:
             del self._mapping[keycode]
             self.changed = True
 
-    @update_reverse_mapping
+    @keep_reverse_mapping_intact
     def empty(self):
         """Remove all mappings."""
         self._mapping = {}
         self.changed = True
 
-    @update_reverse_mapping
+    @keep_reverse_mapping_intact
     def load(self, device, preset):
         """Load a dumped JSON from home to overwrite the mappings."""
         path = get_config_path(device, preset)