Allow to test Jython

METHOD=virtualenv PYTHON=jython VERSION=2.7 ./smoke/venv.sh

smoke/venv.sh

@@ -34,7 +34,10 @@ if [ "$VERSION" == "2.6" ]; then
     pip install pytest
     pip install Cython --install-option="--no-cython-compile"
 else
-    python -m pip install pytest Cython
+    python -m pip install pytest
+    if [ "$PYTHON" != "jython" ]; then
+        python -m pip install Cython
+    fi
 fi
 
 # run tests
@@ -46,6 +49,7 @@ EOF
 python -m pytest -v test_foo.py
 
 # check that we can do extension modules
+if [ "$PYTHON" != "jython" ]; then
 cat > module.pyx << EOF
 cdef int add(int a, int b):
     return a + b
@@ -66,6 +70,7 @@ EOF
 python setup.py build_ext --inplace
 
 python -c 'import module; print(module.two())' | grep '^2$'
+fi
 
 # deactivate has unset variable, it's known
 set +u