Add Sphinx doc building to Travis

.travis.yml

@@ -11,12 +11,17 @@ matrix:
       env: TEST_GMPY="true"
     - python: 3.3
       env: TEST_GMPY="true"
+    - python: 2.7
+      env: TEST_SPHINX="true"
 before_install:
   - if [[ "${TEST_GMPY}" == "true" ]]; then
       sudo apt-get update -qq;
       sudo apt-get install -qq libgmp-dev;
       pip install "gmpy==1.16";
     fi
+  - if [[ "${TEST_SPHINX}" == "true" ]]; then
+      pip install sphinx;
+    fi
 install:
   - if [[ $TRAVIS_PYTHON_VERSION == '3.2' || $TRAVIS_PYTHON_VERSION == '3.3' ]]; then python bin/use2to3; cd py3k-sympy; fi
   - python setup.py install

bin/test_travis.sh

@@ -2,17 +2,22 @@
 
 set -e
 
-# We change directories to make sure that we test the installed version of
-# sympy.
-mkdir empty
-cd empty
-cat << EOF | python
+if [[ "${TEST_SPHINX}" == "true" ]]; then
+    cd doc
+    make html-errors
+else
+    # We change directories to make sure that we test the installed version of
+    # sympy.
+    mkdir empty
+    cd empty
+    cat << EOF | python
 import sympy
 t1=sympy.test()
 t2=sympy.doctest()
 if not (t1 and t2):
     raise Exception('Tests failed')
 EOF
 
-cd ..
-bin/doctest doc/
+    cd ..
+    bin/doctest doc/
+fi