package: test also docstring validity.

Doctest is ... wow. Such a simple idea and yet so useful. No need to do
any complex compiled code snippets like with C++.

package/archlinux/PKGBUILD

@@ -34,6 +34,9 @@ check() {
 
     cd "$_rootdir/src/python/magnum"
     python -m unittest -v
+
+    cd "$_rootdir/doc/python"
+    PYTHONPATH="$_rootdir/build/src/python" python -m doctest -v *.rst
 }
 
 package() {

package/ci/travis-desktop-gles.sh

@@ -74,3 +74,7 @@ coverage run -m unittest -v && cp .coverage ../.coverage.corrade
 
 cd ../magnum
 coverage run -m unittest -v && cp .coverage ../.coverage.magnum
+
+# Test docstring validity
+cd ../../../doc/python
+PYTHONPATH="$TRAVIS_BUILD_DIR/build/src/python" python3 -m doctest -v *.rst

package/ci/travis-desktop.sh

@@ -63,3 +63,7 @@ coverage run -m unittest -v && cp .coverage ../.coverage.corrade
 
 cd ../magnum
 coverage run -m unittest -v && cp .coverage ../.coverage.magnum
+
+# Test docstring validity
+cd ../../../doc/python
+PYTHONPATH="$TRAVIS_BUILD_DIR/build/src/python" python3 -m doctest -v *.rst