Add black to travis checking

.travis.yml

@@ -4,10 +4,12 @@ compiler: gcc
 addons:
   apt:
     sources:
+      - deadsnakes
       - ubuntu-toolchain-r-test
     packages:
       - gcc-7
       - cppcheck
+      - python3.6
 script:
   - export CC=gcc-7
   - make test

Makefile

@@ -69,22 +69,25 @@ uECC.o: ./crypto/micro-ecc/uECC.c
 
 env2:
 	virtualenv --python=python2.7 env2
-	env2/bin/pip install --upgrade -r tools/requirements.txt
+	env3/bin/pip --version
+	env2/bin/pip install -r tools/requirements.txt
 
 env3:
-	python3 -m venv env3
-	env3/bin/pip install --upgrade -r tools/requirements.txt
-	env3/bin/pip install --upgrade black
+	# black requires >=py3.6
+	virtualenv --python=python3.6 env3 
+	env3/bin/pip --version
+	env3/bin/pip install -r tools/requirements.txt
+	env3/bin/pip install black
 
+.PHONY: black blackcheck wink2 wink3 fido2-test cppcheck test clean
 # selectively reformat our own code
-black: env3
-	env3/bin/black --skip-string-normalization tools/
 
-wink2: env2
-	env2/bin/python tools/solotool.py solo --wink
+blackcheck: export BLACK_CHECK_FLAG := --check
+black blackcheck: env3
+	env3/bin/black --skip-string-normalization $(BLACK_CHECK_FLAG) tools/
 
-wink3: env3
-	env3/bin/python tools/solotool.py solo --wink
+wink2 wink3: wink% : env%
+	$</bin/python tools/solotool.py solo --wink
 
 fido2-test: env3
 	env3/bin/python tools/ctap_test.py
@@ -97,7 +100,7 @@ cppcheck:
 	cppcheck $(CPPCHECK_FLAGS) fido2
 	cppcheck $(CPPCHECK_FLAGS) pc
 
-test: main cppcheck
+test: main cppcheck blackcheck
 
 clean:
 	rm -f *.o main.exe main $(obj)