Merge pull request readthedocs#5366 from stsewd/start-building-with-sphinx-18

Start building with sphinx 1.8

Author: stsewd

readthedocs/doc_builder/python_environments.py

@@ -303,7 +303,7 @@ def install_core_requirements(self):
                 self.project.get_feature_value(
                     Feature.USE_SPHINX_LATEST,
                     positive='sphinx<2',
-                    negative='sphinx<1.8',
+                    negative='sphinx<2',
                 ),
                 'sphinx-rtd-theme<0.5',
                 'readthedocs-sphinx-ext<0.6',