swtich matplotlib backend to agg by default

gitlab/functions.sh

@@ -440,3 +440,8 @@ LANG="en_US.UTF-8"
 LC_ALL="${LANG}"
 export_env LANG
 export_env LC_ALL
+
+# Set up the location of matplotlibrc:
+# https://matplotlib.org/users/customizing.html#the-matplotlibrc-file
+MATPLOTLIBRC="_ci"
+export_env MATPLOTLIBRC

gitlab/install.sh

@@ -61,6 +61,7 @@ get_script ${1} cacert.pem
 get_script ${1} functions.sh
 get_script ${1} conda_build_config.yaml
 get_script ${1} recipe_append.yaml
+get_script ${1} matplotlibrc
 get_exec ${1} before_build.sh
 for stage in "build" "deploy" "pypi"; do
   get_exec ${1} ${stage}.sh

gitlab/matplotlibrc

+backend      : agg