[MXAPPS-581] Straight Dope nightly fixes. (#11934)

Enable 3 notebooks that were failing tests after making updates to the
Straight Dope book. We also add pandas required by one of these
notebooks.

ci/docker/install/ubuntu_nightly_tests.sh

@@ -30,3 +30,8 @@ apt-get -y install time
 
 # Install for RAT License Check Nightly Test
 apt-get install -y subversion maven -y #>/dev/null
+
+# Packages needed for the Straight Dope Nightly tests.
+pip2 install pandas
+pip3 install pandas
+

tests/nightly/straight_dope/test_notebooks_single_gpu.py

@@ -89,9 +89,8 @@ def test_linear_algebra(self):
     def test_probability(self):
         assert _test_notebook('chapter01_crashcourse/probability')
 
-    # TODO(vishaalk): Notebook contains the word 'Warning'. Needs to be updated to a synonym.
-    #def test_autograd(self):
-    #    assert _test_notebook('chapter01_crashcourse/autograd')
+    def test_autograd(self):
+        assert _test_notebook('chapter01_crashcourse/autograd')
 
     # Chapter 2
 
@@ -113,9 +112,8 @@ def test_softmax_regression_gluon(self):
     def test_regularization_scratch(self):
         assert _test_notebook('chapter02_supervised-learning/regularization-scratch')
 
-    # TODO(vishaalk): Notebook does not appear to be JSON: '{\n "cells": [\n  {\n   "cell_type": "m....
-    #def test_regularization_gluon(self):
-    #    assert _test_notebook('chapter02_supervised-learning/regularization-gluon')
+    def test_regularization_gluon(self):
+        assert _test_notebook('chapter02_supervised-learning/regularization-gluon')
 
     def test_perceptron(self):
         assert _test_notebook('chapter02_supervised-learning/perceptron')
@@ -258,9 +256,8 @@ def test_tree_lstm(self):
     def test_lds_scratch(self):
         assert _test_notebook('chapter12_time-series/lds-scratch')
 
-    # TODO(vishaalk): File doesn't appear to be valid JSON.
-    #def test_issm_scratch(self):
-    #    assert _test_notebook('chapter12_time-series/issm-scratch')
+    def test_issm_scratch(self):
+        assert _test_notebook('chapter12_time-series/issm-scratch')
 
     # Chapter 14
 
@@ -273,7 +270,7 @@ def test_dcgan(self):
     def test_generative_adversarial_networks(self):
         assert _test_notebook('chapter14_generative-adversarial-networks/conditional')
 
-    # TODO(vishaalk): Notebook does not appear to be valid JSON.
+    # TODO(vishaalk): Investigate.
     #def test_pixel2pixel(self):
     #    assert _test_notebook('chapter14_generative-adversarial-networks/pixel2pixel')