Meta: Resolve some pylint violations in Python lint scripts

Resolves:

* all: consider-using-sys-exit
* all: wrong-import-order
* all: TODO: Require that a few keys are set? (fixme)
* some: missing-function-docstring
* some: line-too-long

Meta/lint-keymaps.py

@@ -2,7 +2,7 @@
 
 import json
 import os
-
+import sys
 
 PERMITTED_MAPS = ['map', 'shift_map', 'alt_map', 'altgr_map', 'shift_altgr_map']
 REQUIRED_MAPS = ['map', 'shift_map', 'alt_map']
@@ -12,10 +12,27 @@ GOOD_MAP_LENGTHS = {90, 128}
 
 
 def report(filename, problem):
+    """Print a lint problem to stdout.
+
+    Args:
+        filename (str): keymap file name
+        problem (str): problem message
+    """
     print('{}: {}'.format(filename, problem))
 
 
 def validate_single_map(filename, mapname, values):
+    """Validate a key map.
+
+    Args:
+        filename (str): keymap file name
+        mapname (str): map name (altgr_map, alt_map, shift_altgr_map)
+        values (list): key values
+
+    Returns:
+        bool: key map is valid
+    """
+
     all_good = True
 
     if not isinstance(values, list):
@@ -31,7 +48,9 @@ def validate_single_map(filename, mapname, values):
             report(filename, 'more than one character ("{}") for charmap index {} of {}'.format(c, i, mapname))
             all_good = False
 
-    # TODO: Require that a few keys are set?
+    if len(values) == 0:
+        report(filename, 'map {} is empty.'.format(mapname))
+        all_good = False
 
     if len(values) not in GOOD_MAP_LENGTHS:
         report(filename, 'length {} of map {} is suspicious. Off-by-one?'.format(len(values), mapname))
@@ -41,6 +60,16 @@ def validate_single_map(filename, mapname, values):
 
 
 def validate_fullmap(filename, fullmap):
+    """Validate a full key map for all map names (including maps for key modifiers).
+
+    Args:
+        filename (str): keymap file name
+        fullmap (dict): key mappings
+
+    Returns:
+        bool: keymap file contains valid key mappings
+    """
+
     all_good = True
 
     if not isinstance(fullmap, dict):
@@ -73,6 +102,15 @@ def validate_fullmap(filename, fullmap):
 
 
 def run_with(filenames):
+    """Check list of keymap files for errors.
+
+    Args:
+        filenames (list): keymap files to check
+
+    Returns:
+        bool: All keymap files are valid
+    """
+
     passed = 0
     for filename in filenames:
         with open(filename, 'r') as fp:
@@ -85,6 +123,12 @@ def run_with(filenames):
 
 
 def list_files_here():
+    """Retrieve a list of all '.json' files in the working directory.
+
+    Returns:
+        list: JSON file names
+    """
+
     filelist = []
     for filename in os.listdir():
         if filename.endswith('.json'):
@@ -98,10 +142,16 @@ def list_files_here():
 
 
 def run_here():
+    """Check all keymap files in the working directory for errors.
+
+    Returns:
+        bool: All keymap files are valid
+    """
+
     return run_with(list_files_here())
 
 
 if __name__ == '__main__':
     os.chdir(os.path.dirname(__file__) + "/../Base/res/keymaps/")
     if not run_here():
-        exit(1)
+        sys.exit(1)