Conditional dependency on futures (#682)

setup.py

@@ -1,4 +1,3 @@
-import sys
 from codecs import open
 from os import path
 
@@ -11,24 +10,6 @@ here = path.abspath(path.dirname(__file__))
 with open(path.join(here, 'DESCRIPTION.rst'), encoding='utf-8') as f:
     long_description = f.read()
 
-install_requires = [
-    'gitpython>=1.0, <2.0',
-    'jsonschema==2.4',  # pin the exact version, jsonschema 2.5 broke py3
-    'pager>=3.3, <4.0',
-    'portalocker>=0.5, <1.0',
-    'prettytable>=0.7, <1.0',
-    'pygments>=2.0, <3.0',
-    'pypng==0.0.18',
-    'pystache>=0.5, <1.0',
-    'requests>=2.6, <3.0',
-    'six>=1.9, <2.0',
-    'toml>=0.9, <1.0',
-]
-
-if sys.version_info[0] == 2:
-    install_requires.append('futures>=3.0, <4.0')
-
-
 setup(
     name='dcos',
 
@@ -77,11 +58,23 @@ setup(
     # simple. Or you can use find_packages().
     packages=find_packages(exclude=['pydoc', 'tests', 'cli', 'bin']),
 
-    # List run-time dependencies here.  These will be installed by pip when
-    # your project is installed. For an analysis of "install_requires" vs pip's
-    # requirements files see:
-    # https://packaging.python.org/en/latest/requirements.html
-    install_requires=install_requires,
+    install_requires=[
+        'gitpython>=1.0, <2.0',
+        'jsonschema==2.4',  # pin the exact version, jsonschema 2.5 broke py3
+        'pager>=3.3, <4.0',
+        'portalocker>=0.5, <1.0',
+        'prettytable>=0.7, <1.0',
+        'pygments>=2.0, <3.0',
+        'pypng==0.0.18',
+        'pystache>=0.5, <1.0',
+        'requests>=2.6, <3.0',
+        'six>=1.9, <2.0',
+        'toml>=0.9, <1.0',
+    ],
+
+    extras_require={
+        ':python_version=="2.7"': ['futures>=3.0, <4.0'],
+    },
 
     package_data={
         'dcos': [