circle: set locale to a UTF-8 variant so python doesn't fall back to ascii

.circleci/config.yml

@@ -10,11 +10,12 @@ jobs:
     environment:
       - PYTHONIOENCODING: utf-8
     steps:
-      - run: apt-get update ; apt-get install -y make git curl python3 python3-pip wget imagemagick
+      - run: apt-get update ; apt-get install -y make git curl python3 python3-pip wget imagemagick locales
+      - run: locale-gen "en_US.UTF-8"; update-locale LC_ALL="en_US.UTF-8"
       - checkout
       - run: make install PIP_INSTALL="pip3 install"
       - run: pip3 install -r requirements-test.txt
-      - run: make coverage
+      - run: make coverage LC_ALL=en_US.utf8
       - codecov/upload
 
 workflows:

Makefile

@@ -1,3 +1,4 @@
+export  # export variables to subshells
 PIP_INSTALL = pip3 install
 GIT_CLONE = git clone
 PYTHON = python3