@@ -1815,7 +1815,7 @@ def normalize_kwargs(kw, alias_mapping=None, required=(), forbidden=(),
                         "are in kwargs".format(keys=fail_keys))
 
     if allowed is not None:
-        allowed_set = set(required) | set(allowed)
+        allowed_set = {*required, *allowed}
         fail_keys = [k for k in ret if k not in allowed_set]
         if fail_keys:
             raise TypeError(
 
@@ -65,16 +65,16 @@ def get_unicode_index(symbol, math=True):
     # length, usually longer than a hyphen.
     if symbol == '-':
         return 0x2212
-    try:# This will succeed if symbol is a single unicode char
+    try:  # This will succeed if symbol is a single unicode char
         return ord(symbol)
     except TypeError:
         pass
-    try:# Is symbol a TeX symbol (i.e. \alpha)
+    try:  # Is symbol a TeX symbol (i.e. \alpha)
         return tex2uni[symbol.strip("\\")]
     except KeyError:
-        message = """'%(symbol)s' is not a valid Unicode character or
-TeX/Type1 symbol"""%locals()
-        raise ValueError(message)
+        raise ValueError(
+            "'{}' is not a valid Unicode character or TeX/Type1 symbol"
+            .format(symbol))
 
 
 unichr_safe = cbook.deprecated("3.0")(chr)
 
@@ -63,7 +63,7 @@ def __call__(self, s):
             s = s.lower()
         if s in self.valid:
             return self.valid[s]
-        raise ValueError('Unrecognized %s string "%s": valid strings are %s'
+        raise ValueError('Unrecognized %s string %r: valid strings are %s'
                          % (self.key, s, list(six.itervalues(self.valid))))
 
 
@@ -935,25 +935,13 @@ def _validate_linestyle(ls):
     A validator for all possible line styles, the named ones *and*
     the on-off ink sequences.
     """
-    # Look first for a valid named line style, like '--' or 'solid'
-    if isinstance(ls, six.string_types):
-        try:
-            return _validate_named_linestyle(ls)
-        except (UnicodeDecodeError, KeyError):
-            # On Python 2, string-like *ls*, like for example
-            # 'solid'.encode('utf-16'), may raise a unicode error.
-            raise ValueError("the linestyle string {!r} is not a valid "
-                             "string.".format(ls))
-
-    if isinstance(ls, (bytes, bytearray)):
-        # On Python 2, a string-like *ls* should already have lead to a
-        # successful return or to raising an exception. On Python 3, we have
-        # to manually raise an exception in the case of a byte-like *ls*.
-        # Otherwise, if *ls* is of even-length, it will be passed to the
-        # instance of validate_nseq_float, which will return an absurd on-off
-        # ink sequence...
-        raise ValueError("linestyle {!r} neither looks like an on-off ink "
-                         "sequence nor a valid string.".format(ls))
+    # Look first for a valid named line style, like '--' or 'solid' Also
+    # includes bytes(-arrays) here (they all fail _validate_named_linestyle);
+    # otherwise, if *ls* is of even-length, it will be passed to the instance
+    # of validate_nseq_float, which will return an absurd on-off ink
+    # sequence...
+    if isinstance(ls, (str, bytes, bytearray)):
+        return _validate_named_linestyle(ls)
 
     # Look for an on-off ink sequence (in points) *of even length*.
     # Offset is set to None.
 
@@ -917,7 +917,7 @@ def on_text_change(self, func):
 
     def on_submit(self, func):
         """
-        When the user hits enter or leaves the submision box, call this
+        When the user hits enter or leaves the submission box, call this
         *func* with event.
 
         A connection id is returned which can be used to disconnect.
@@ -928,8 +928,8 @@ def on_submit(self, func):
         return cid
 
     def disconnect(self, cid):
-        """remove the observer with connection id *cid*"""
-        for reg in (self.change_observers, self.submit_observers):
+        """Remove the observer with connection id *cid*."""
+        for reg in [self.change_observers, self.submit_observers]:
             try:
                 del reg[cid]
             except KeyError:
 
@@ -284,11 +284,7 @@ def __init__(self):
         if sys.platform == 'win32':
             self.has_pkgconfig = False
         else:
-            try:
-                self.pkg_config = os.environ['PKG_CONFIG']
-            except KeyError:
-                self.pkg_config = 'pkg-config'
-
+            self.pkg_config = os.environ.get('PKG_CONFIG', 'pkg-config')
             self.set_pkgconfig_path()
             self.has_pkgconfig = shutil.which(self.pkg_config) is not None
             if not self.has_pkgconfig:
 
@@ -1,17 +1,12 @@
 """Functions for Github API requests."""
 
-try:
-    input = raw_input
-except NameError:
-    pass
-
+import getpass
+import json
 import os
 import re
 import sys
 
 import requests
-import getpass
-import json
 
 try:
     import requests_cache