Fix flake8 issues

This commit contains a very large number of trivial changes in order to fix flake8 errors and warnings.  Predominantly these are whitespace changes.

Additionally, the build for Python 3.7 on TravisCI has been tweaked to fail if there are any flake8 errors using the following commandline:
* flake8 . --count --ignore=E252 --max-complexity=31 --max-line-length=127 --show-source --statistics
NOTE: In the future the max cyclomatic complexity should be lowered, but some improvements need to be made first.

One flake8 error is being ignored entirely:
* E252 missing whitespace around parameter equals
    * ignored because it doesn't correctly deal with default argument values after a type hint

A few flake8 errors are being selectively ignored in certain files:
* C901 fuction is too complex
    * ignored in argparse_completer.py because the complex code is an override of argparse complexity
* E302 expected 2 blank lines after ...
    * ignored in all unit test files for convenience
* F401 module imported but unused
    * ignored in cmd2/__init__.py because imports are for convenience of cmd2 developers and backwards compatibility
* F821 undefined name
    * ignored in cmd2 script files which are intended to run only within cmd2 applications via pyscript where "app" and "cmd" are defined

1 files changed, 21 insertions, 21 deletions

diff --git a/examples/tab_autocompletion.py b/examples/tab_autocompletion.py
index dad9e90d..1c578c72 100755
--- a/examples/tab_autocompletion.py
+++ b/examples/tab_autocompletion.py
@@ -59,10 +59,10 @@ class TabCompleteExample(cmd2.Cmd):
                                             'Alec Guinness', 'Peter Mayhew', 'Anthony Daniels']
                                   },
                       'SW_EP1': {'title': 'Star Wars: Episode I - The Phantom Menace',
-                                  'rating': 'PG',
-                                  'director': ['George Lucas'],
-                                  'actor': ['Liam Neeson', 'Ewan McGregor', 'Natalie Portman', 'Jake Lloyd']
-                                  },
+                                 'rating': 'PG',
+                                 'director': ['George Lucas'],
+                                 'actor': ['Liam Neeson', 'Ewan McGregor', 'Natalie Portman', 'Jake Lloyd']
+                                 },
                       'SW_EP02': {'title': 'Star Wars: Episode II - Attack of the Clones',
                                   'rating': 'PG',
                                   'director': ['George Lucas'],
@@ -79,21 +79,21 @@ class TabCompleteExample(cmd2.Cmd):
                       }
     USER_SHOW_LIBRARY = {'SW_REB': ['S01E01', 'S02E02']}
     SHOW_DATABASE_IDS = ['SW_CW', 'SW_TCW', 'SW_REB']
-    SHOW_DATABASE = {'SW_CW':   {'title': 'Star Wars: Clone Wars',
-                                 'rating': 'TV-Y7',
-                                 'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
-                                             2: ['S02E01', 'S02E02', 'S02E03']}
-                                 },
-                     'SW_TCW':  {'title': 'Star Wars: The Clone Wars',
-                                 'rating': 'TV-PG',
-                                 'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
-                                             2: ['S02E01', 'S02E02', 'S02E03']}
-                                 },
-                     'SW_REB':  {'title': 'Star Wars: Rebels',
-                                 'rating': 'TV-Y7',
-                                 'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
-                                             2: ['S02E01', 'S02E02', 'S02E03']}
-                                 },
+    SHOW_DATABASE = {'SW_CW': {'title': 'Star Wars: Clone Wars',
+                               'rating': 'TV-Y7',
+                               'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
+                                           2: ['S02E01', 'S02E02', 'S02E03']}
+                               },
+                     'SW_TCW': {'title': 'Star Wars: The Clone Wars',
+                                'rating': 'TV-PG',
+                                'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
+                                            2: ['S02E01', 'S02E02', 'S02E03']}
+                                },
+                     'SW_REB': {'title': 'Star Wars: Rebels',
+                                'rating': 'TV-Y7',
+                                'seasons': {1: ['S01E01', 'S01E02', 'S01E03'],
+                                            2: ['S02E01', 'S02E02', 'S02E03']}
+                                },
                      }
 
     file_list = \
@@ -299,7 +299,8 @@ class TabCompleteExample(cmd2.Cmd):
                               ', '.join(movie['director']),
                               '\n    '.join(movie['actor'])))
         elif args.command == 'add':
-            print('Adding Movie\n----------------\nTitle: {}\nRating: {}\nDirectors: {}\nActors: {}\n\n'.format(args.title, args.rating, ', '.join(args.director), ', '.join(args.actor)))
+            print('Adding Movie\n----------------\nTitle: {}\nRating: {}\nDirectors: {}\nActors: {}\n\n'
+                  .format(args.title, args.rating, ', '.join(args.director), ', '.join(args.actor)))
 
     def _do_media_shows(self, args) -> None:
         if not args.command:
@@ -367,7 +368,6 @@ class TabCompleteExample(cmd2.Cmd):
             # No subcommand was provided, so call help
             self.do_help('media')
 
-
     # This completer is implemented using a single dictionary to look up completion lists for all layers of
     # subcommands. For each argument, AutoCompleter will search for completion values from the provided
     # arg_choices dict. This requires careful naming of argparse arguments so that there are no unintentional