update testing settings

Author: willforde

setup.py

@@ -22,27 +22,32 @@ def version(name):
             raise RuntimeError("Unable to extract version number")
 
 
-setup(name='htmlement',
-      version=version('htmlement.py'),
-      description='Pure-Python HTML parser with ElementTree support.',
-      long_description=readme(),
-      keywords='html html5 parsehtml htmlparser elementtree dom',
-      classifiers=['Development Status :: 5 - Production/Stable',
-                   'Intended Audience :: Developers',
-                   'License :: OSI Approved :: MIT License',
-                   'Natural Language :: English',
-                   'Operating System :: OS Independent',
-                   'Programming Language :: Python :: 2',
-                   'Programming Language :: Python :: 2.7',
-                   'Programming Language :: Python :: 3',
-                   'Programming Language :: Python :: 3.4',
-                   'Programming Language :: Python :: 3.5',
-                   'Programming Language :: Python :: 3.6',
-                   'Topic :: Text Processing :: Markup :: HTML',
-                   'Topic :: Software Development :: Libraries :: Python Modules'],
-      url='https://github.com/willforde/python-htmlement',
-      platforms=['OS Independent'],
-      author='William Forde',
-      author_email='[email protected]',
-      license='MIT License',
-      py_modules=['htmlement'])
+setup(
+    name='htmlement',
+    version=version('htmlement.py'),
+    description='Pure-Python HTML parser with ElementTree support.',
+    long_description=readme(),
+    extras_require={"dev": ["pytest", "pytest-cov"]},
+    keywords='html html5 parsehtml htmlparser elementtree dom',
+    classifiers=[
+        'Development Status :: 5 - Production/Stable',
+        'Intended Audience :: Developers',
+        'License :: OSI Approved :: MIT License',
+        'Natural Language :: English',
+        'Operating System :: OS Independent',
+        'Programming Language :: Python :: 2',
+        'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
+        'Topic :: Text Processing :: Markup :: HTML',
+        'Topic :: Software Development :: Libraries :: Python Modules'
+    ],
+    url='https://github.com/willforde/python-htmlement',
+    platforms=['OS Independent'],
+    author='William Forde',
+    author_email='[email protected]',
+    license='MIT License',
+    py_modules=['htmlement']
+)

tox.ini

@@ -1,11 +1,24 @@
 [tox]
-envlist = py{27,34,35,36,37}
-skip_missing_interpreters=true
+envlist = py{27,36,37,38,39},flake8
+skip_missing_interpreters = true
 
 [testenv]
-deps=
-  pytest
-  pytest-cov
+extras = dev
+commands = py.test --cov
 
-commands=
-  py.test --cov
+# Flake8 Environment
+[testenv:flake8]
+basepython = python3
+skip_install = true
+deps =
+    flake8
+commands =
+    flake8 --max-line-length=120
+
+# Flake8 Configuration
+[flake8]
+exclude =
+    .tox,
+    .git,
+    docs,
+    tests