Tox.ini; Test on Python 3.9 and make flake8 stricter (#966)

* Tox.ini; Test on Python 3.9 and make flake8 stricter

* max-line-length = 88

* Remove unused import

* Update tox.ini

* Use PEP8 line length

* Use PEP8 line length
diff --git a/doc/conf.py b/doc/conf.py
index cb699c8..dd8d011 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -3,7 +3,7 @@
 # pyOpenSSL documentation build configuration file, created by
 # sphinx-quickstart on Sat Jul 16 07:12:22 2011.
 #
-# This file is execfile()d with the current directory set to its containing dir.
+# This file is execfile()d with the current directory set to its parent dir.
 #
 # Note that not all possible configuration values are present in this
 # autogenerated file.
@@ -11,7 +11,6 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import datetime
 import codecs
 import os
 import re
@@ -48,7 +47,7 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 # sys.path.insert(0, os.path.abspath('.'))
 
-# -- General configuration -----------------------------------------------------
+# -- General configuration ----------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
 needs_sphinx = "1.0"
@@ -100,7 +99,7 @@
 # directories to ignore when looking for source files.
 exclude_patterns = ["_build"]
 
-# The reST default role (used for this markup: `text`) to use for all documents.
+# The reST default role (used for this markup `text`) to use for all documents.
 # default_role = None
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
@@ -121,7 +120,7 @@
 # modindex_common_prefix = []
 
 
-# -- Options for HTML output ---------------------------------------------------
+# -- Options for HTML output --------------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
@@ -207,7 +206,7 @@
 htmlhelp_basename = "pyOpenSSLdoc"
 
 
-# -- Options for LaTeX output --------------------------------------------------
+# -- Options for LaTeX output -------------------------------------------------
 
 # The paper size ('letter' or 'a4').
 # latex_paper_size = 'letter'
@@ -216,7 +215,7 @@
 # latex_font_size = '10pt'
 
 # Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title, author, documentclass [howto/manual]).
+# (source start file, target name, title, author, documentclass [howto/manual])
 latex_documents = [
     ("index", "pyOpenSSL.tex", u"pyOpenSSL Documentation", authors, "manual"),
 ]
@@ -245,7 +244,7 @@
 # latex_domain_indices = True
 
 
-# -- Options for manual page output --------------------------------------------
+# -- Options for manual page output -------------------------------------------
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).