Try and run some python tests in Travis

.travis.yml

@@ -1,12 +1,16 @@
-dist: trusty
+sudo: required
-language: c
+dist: bionic
-compiler: gcc
+language: generic
-addons:
+compiler:
-  apt:
+  - clang
-    sources:
+  - gcc
-      - ubuntu-toolchain-r-test
+cache: pip
-    packages:
+
-      - gcc-7
+install:
+  - pip install -f tools/requirements.txt
+  - pip install black
+
 script:
-  - export CC=gcc-7
+  - env3/bin/black --check --skip-string-normalization tools/
+  - env3/bin/python tools/solotool.py -h
   - make test

Makefile

@@ -81,7 +81,7 @@ env3:
 
 # selectively reformat our own code
 black: env3
-	env3/bin/black -S tools/
+	env3/bin/black --skip-string-normalization tools/
 
 wink2: env2
 	env2/bin/python tools/solotool.py solo --wink