test with presence and absence of unidecode

.travis.yml

@@ -5,9 +5,14 @@ python:
     - "3.8"
     - "3.9-dev"
 
-# command to install dependencies
+env:
+    - variant=1
+    - variant=2
+
+
 install:
-    - pip install .[gpl]
+    - if [ "$variant" = "1" ]; then pip install .; fi
+    - if [ "$variant" = "2" ]; then pip install .[gpl]; fi
 
 script: pytest