also run tests with cu2qu compiled with cython

.travis.yml

@@ -26,6 +26,8 @@ matrix:
       env: TOXENV=py37-cov
     - python: 3.8
       env: TOXENV=py38-cov
+    - python: 3.8
+      env: TOXENV=py38-cy
     - python: pypy3
       # disable coverage.py on pypy because of performance problems
       env: TOXENV=pypy3

tox.ini

@@ -3,9 +3,11 @@ minversion = 3.0
 envlist = py3{6,7,8}-cov, htmlcov
 
 [testenv]
+setenv =
+    cy: FONTTOOLS_WITH_CYTHON=1
 deps =
     cov: coverage>=4.3
-    pytest==5.1.1
+    pytest
     pytest-randomly
     -rrequirements.txt
 extras =
@@ -15,6 +17,8 @@ extras =
     interpolatable
     !nolxml: lxml
 commands =
+    cy: python -c "from fontTools.cu2qu.cu2qu import COMPILED; assert COMPILED"
+    !cy: python -c "from fontTools.cu2qu.cu2qu import COMPILED; assert not COMPILED"
     # test with or without coverage, passing extra positonal args to pytest
     cov: coverage run --parallel-mode -m pytest {posargs:Tests fontTools}
     !cov: pytest {posargs:Tests fontTools}