Attempt: env vars listed in coveralls docs

This is an attempt to fix #449

According to https://docs.coveralls.io/supported-ci-services

There is a list of env variables that, when set, are supposed to add
support to any arbitrary CI.

.cirrus.yml

@@ -4,12 +4,22 @@ auto_cancellation: false
 env:
   PATH: ${HOME}/.local/bin:${PATH}
   # ^  add user paths
-  COVERALLS_REPO_TOKEN: ENCRYPTED[7ada9fe1105610d2b5ac314f5eb4cc2fea3d42a5fa1e1bfa263000277146022b71b80f7d2f00dc6058e08bd1c9034be7]
   PIP_CACHE: ${HOME}/.cache/pip
   PRE_COMMIT_HOME: ${HOME}/.cache/pre-commit
   LC_ALL: C.UTF-8
   LANG: C.UTF-8
   COVERAGE: NO
+  # Coveralls config
+  COVERALLS_SERVICE_NAME: cirrus-ci
+  COVERALLS_SERVICE_JOB_NUMBER: ${CIRRUS_BUILD_ID}
+  # COVERALLS_REPO_TOKEN: ENCRYPTED[7ada9fe1105610d2b5ac314f5eb4cc2fea3d42a5fa1e1bfa263000277146022b71b80f7d2f00dc6058e08bd1c9034be7]
+  CI_NAME: cirrus-ci
+  CI_BUILD_NUMBER: ${CIRRUS_BUILD_ID}
+  CI_BUILD_URL: https://cirrus-ci.com/build/${CIRRUS_BUILD_ID}
+  CI_JOB_ID: ${CIRRUS_TASK_ID}
+  CI_BRANCH: ${CIRRUS_BRANCH}
+  CI_PULL_REQUEST: ${CIRRUS_PR}
+
 
 # This template is used in most of the tasks
 .regular_task_template: &REGULAR_TASK_TEMPLATE