Fix readthedocs

setup.py

@@ -29,10 +29,11 @@ setup(
         'Source': 'https://github.com/plamere/spotipy',
     },
     install_requires=[
-        'redis>=3.5.3',
-        'requests>=2.25.0',
-        'six>=1.15.0',
-        'urllib3>=1.26.0'
+        "redis>=3.5.3",
+        "redis<4.0.0;python_version<'3.4'",
+        "requests>=2.25.0",
+        "six>=1.15.0",
+        "urllib3>=1.26.0"
     ],
     tests_require=test_reqs,
     extras_require=extra_reqs,