Convert to use CircleCI and run tests against Django 2.1/Python 3.7

setup.py

@@ -1,13 +1,39 @@
 import os
+import distutils.cmd
+import subprocess
 
 from setuptools import find_packages, setup
 
+
+class BaseCommand(distutils.cmd.Command):
+    user_options = []
+
+    def initialize_options(self):
+        pass
+
+    def finalize_options(self):
+        pass
+
+
+def create_command(text, commands):
+    """Creates a custom setup.py command."""
+
+    class CustomCommand(BaseCommand):
+        description = text
+
+        def run(self):
+            for cmd in commands:
+                subprocess.check_call(cmd)
+
+    return CustomCommand
+
+
 with open(os.path.join(os.path.dirname(__file__), 'README.rst'), encoding='utf-8') as readme:
     README = readme.read()
 
 setup(
     name='django-localized-fields',
-    version='5.0a3',
+    version='5.0a5',
     packages=find_packages(exclude=['tests']),
     include_package_data=True,
     license='MIT License',
@@ -18,7 +44,7 @@ setup(
     author_email='open-source@sectorlabs.ro',
     keywords=['django', 'localized', 'language', 'models', 'fields'],
     install_requires=[
-        'django-postgres-extra>=1.21a11',
+        'django-postgres-extra>=1.21a14',
         'Django>=1.11',
         'deprecation==2.0.3'
     ],
@@ -32,5 +58,11 @@ setup(
         'Programming Language :: Python :: 3.5',
         'Topic :: Internet :: WWW/HTTP',
         'Topic :: Internet :: WWW/HTTP :: Dynamic Content',
-    ]
+    ],
+    cmdclass={
+        'lint': create_command(
+            'Lints the code',
+            [['flake8', 'setup.py', 'localized_fields', 'tests']],
+        ),
+    },
 )