Treat warnings as errors when building documentation. (#631)

Author: nadiaya

.readthedocs.yml

@@ -0,0 +1,16 @@
+# ReadTheDocs environment customization to allow us to use conda to install
+# libraries which have C dependencies for the doc build. See:
+# https://docs.readthedocs.io/en/latest/config-file/v2.html
+
+version: 2
+
+python:
+  version: 3.6
+  install:
+    - method: pip
+      path: .
+    - requirements: doc/requirements.txt
+
+sphinx:
+  configuration: doc/conf.py
+  fail_on_warning: true # http://www.sphinx-doc.org/en/master/man/sphinx-build.html#id6

.rtd-environment.yml

@@ -0,0 +1,4 @@
+sphinx==1.7.9
+numpy
+scipy
+requests==2.20

doc/requirements.txt

@@ -357,6 +357,7 @@ The following are optional arguments. When you create an ``MXNet`` object, you c
    results in the following inside the container:
 
    .. code::
+
        opt/ml/code
          ├── train.py
          ├── common

doc/using_mxnet.rst

@@ -490,7 +490,7 @@ def hyperparameter_ranges(self):
 
     @property
     def sagemaker_session(self):
-        """Convenience method for accessing the :class:~`sagemaker.session.Session` object associated
+        """Convenience method for accessing the :class:`~sagemaker.session.Session` object associated
         with the estimator for the ``HyperparameterTuner``.
         """
         return self.estimator.sagemaker_session