tst: run datalad fetcher in tests

Author: oesteban

.circleci/config.yml

@@ -75,7 +75,7 @@ jobs:
             pyenv global 3.5.2
             virtualenv venv
             export TEMPLATEFLOW_USE_DATALAD=on
-            unset TEMPLATEFLOW_HOME
+            export TEMPLATEFLOW_HOME=$HOME/templateflow
             pytest --junit-xml=/tmp/tests/datalad.xml --cov templateflow --cov-report xml:/tmp/cov_api_dl.xml \
                    --doctest-modules /tmp/src/templateflow/templateflow/api.py