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

19 files changed, 19 insertions, 0 deletions

diff --git a/tests/pyscript/bar1.py b/tests/pyscript/bar1.py
index 521e2c29..0f2b1e5e 100644
--- a/tests/pyscript/bar1.py
+++ b/tests/pyscript/bar1.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.bar('11', '22')
diff --git a/tests/pyscript/custom_echo.py b/tests/pyscript/custom_echo.py
index 14040e4c..3a79133a 100644
--- a/tests/pyscript/custom_echo.py
+++ b/tests/pyscript/custom_echo.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 custom.cmd_echo = True
 custom.echo('blah!')
diff --git a/tests/pyscript/foo1.py b/tests/pyscript/foo1.py
index d9345354..443282a5 100644
--- a/tests/pyscript/foo1.py
+++ b/tests/pyscript/foo1.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.foo('aaa', 'bbb', counter=3, trueval=True, constval=True)
diff --git a/tests/pyscript/foo2.py b/tests/pyscript/foo2.py
index d3600a60..9aa37105 100644
--- a/tests/pyscript/foo2.py
+++ b/tests/pyscript/foo2.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.foo('11', '22', '33', '44', counter=3, trueval=True, constval=True)
diff --git a/tests/pyscript/foo3.py b/tests/pyscript/foo3.py
index fc0e084a..e4384076 100644
--- a/tests/pyscript/foo3.py
+++ b/tests/pyscript/foo3.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.foo('11', '22', '33', '44', '55', '66', counter=3, trueval=False, constval=False)
diff --git a/tests/pyscript/foo4.py b/tests/pyscript/foo4.py
index e4b7d01c..a601ccd8 100644
--- a/tests/pyscript/foo4.py
+++ b/tests/pyscript/foo4.py
@@ -1,3 +1,4 @@
+# flake8: noqa F821
 app.cmd_echo = True
 result = app.foo('aaa', 'bbb', counter=3)
 out_text = 'Fail'
diff --git a/tests/pyscript/help.py b/tests/pyscript/help.py
index 664c0488..3f24246d 100644
--- a/tests/pyscript/help.py
+++ b/tests/pyscript/help.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.help()
diff --git a/tests/pyscript/help_media.py b/tests/pyscript/help_media.py
index d8d97c42..38c4a2f8 100644
--- a/tests/pyscript/help_media.py
+++ b/tests/pyscript/help_media.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.help('media')
diff --git a/tests/pyscript/media_movies_add1.py b/tests/pyscript/media_movies_add1.py
index 7249c0ef..b5045a39 100644
--- a/tests/pyscript/media_movies_add1.py
+++ b/tests/pyscript/media_movies_add1.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.add('My Movie', 'PG-13', director=('George Lucas', 'J. J. Abrams'))
diff --git a/tests/pyscript/media_movies_add2.py b/tests/pyscript/media_movies_add2.py
index 681095d7..91dbbc6b 100644
--- a/tests/pyscript/media_movies_add2.py
+++ b/tests/pyscript/media_movies_add2.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.add('My Movie', 'PG-13', actor=('Mark Hamill'), director=('George Lucas', 'J. J. Abrams'))
diff --git a/tests/pyscript/media_movies_list1.py b/tests/pyscript/media_movies_list1.py
index edbc2021..505d1f91 100644
--- a/tests/pyscript/media_movies_list1.py
+++ b/tests/pyscript/media_movies_list1.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.list()
diff --git a/tests/pyscript/media_movies_list2.py b/tests/pyscript/media_movies_list2.py
index 5ad01b7b..69e0d3c5 100644
--- a/tests/pyscript/media_movies_list2.py
+++ b/tests/pyscript/media_movies_list2.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media().movies().list()
diff --git a/tests/pyscript/media_movies_list3.py b/tests/pyscript/media_movies_list3.py
index bdbdfceb..c4f0cc1e 100644
--- a/tests/pyscript/media_movies_list3.py
+++ b/tests/pyscript/media_movies_list3.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app('media movies list')
diff --git a/tests/pyscript/media_movies_list4.py b/tests/pyscript/media_movies_list4.py
index 5f7bdaa9..29e98fe7 100644
--- a/tests/pyscript/media_movies_list4.py
+++ b/tests/pyscript/media_movies_list4.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.list(actor='Mark Hamill')
diff --git a/tests/pyscript/media_movies_list5.py b/tests/pyscript/media_movies_list5.py
index fa4efa5b..1c249ebf 100644
--- a/tests/pyscript/media_movies_list5.py
+++ b/tests/pyscript/media_movies_list5.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.list(actor=('Mark Hamill', 'Carrie Fisher'))
diff --git a/tests/pyscript/media_movies_list6.py b/tests/pyscript/media_movies_list6.py
index ef1851cd..c16ae6c5 100644
--- a/tests/pyscript/media_movies_list6.py
+++ b/tests/pyscript/media_movies_list6.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.list(rating='PG')
diff --git a/tests/pyscript/media_movies_list7.py b/tests/pyscript/media_movies_list7.py
index 7c827b7f..d4ca7dca 100644
--- a/tests/pyscript/media_movies_list7.py
+++ b/tests/pyscript/media_movies_list7.py
@@ -1,2 +1,3 @@
+# flake8: noqa F821
 app.cmd_echo = True
 app.media.movies.list(rating=('PG', 'PG-13'))
diff --git a/tests/pyscript/pyscript_dir1.py b/tests/pyscript/pyscript_dir1.py
index 14a70a31..81814d70 100644
--- a/tests/pyscript/pyscript_dir1.py
+++ b/tests/pyscript/pyscript_dir1.py
@@ -1,3 +1,4 @@
+# flake8: noqa F821
 out = dir(app)
 out.sort()
 print(out)
diff --git a/tests/pyscript/pyscript_dir2.py b/tests/pyscript/pyscript_dir2.py
index 28c61c8e..ebbbf712 100644
--- a/tests/pyscript/pyscript_dir2.py
+++ b/tests/pyscript/pyscript_dir2.py
@@ -1,3 +1,4 @@
+# flake8: noqa F821
 out = dir(app.media)
 out.sort()
 print(out)