Handle maxfail pytest option from InfraRed plugin

This allows to specify PyTest options depending on the workflow step
For instance in the faults workflow step below option is used:
  --maxfail 1

The option can be forced for all speps with below InfraRed plugin option:

 --pytest-maxfail <N>

For more details about pytest options please have a look to pytest help page:

  tox -e py3 -- --help

Change-Id: I3146819b5f80fa4768ea38032cc8e69dc7b44f18

roles/tobiko-tox/defaults/main.yaml

@@ -20,8 +20,10 @@ tox_run_tests_timeout: 18000  # 5 hours
 tox_constraints: ''
 
 tox_constrain_env:
-  PYTEST_ADDOPTS:
-    "{% if not test_flaky %}-m 'not flaky' {% endif %}{{ pytest_addopts }}"
+  PYTEST_ADDOPTS: >
+     {% if not test_flaky%}-m 'not flaky'{% endif %}
+     {% if pytest_maxfail %}--maxfail '{{ pytest_maxfail }}'{% endif %}
+     {{ pytest_addopts }}
   TOX_REPORT_DIR: '{{ tox_report_dir }}'
   TOX_REPORT_NAME: '{{ tox_report_name }}'
   TOX_CONSTRAINTS: '{{ tox_constraints }}'
@@ -35,4 +37,5 @@ tox_expected_rcs:
 ignore_test_failures: no
 
 pytest_addopts: ''
+pytest_maxfail: ''
 test_flaky: false

roles/tobiko-tox/tasks/tox.yaml

@@ -13,9 +13,17 @@
     tox_command_line: '{{ tox_command_line.split() | join(" ") }}'
 
 
-- name: combine environment variables
+- name: combine and normalize environment variable values
   set_fact:
-    tox_env: '{{ tox_environment | from_yaml | combine(tox_constrain_env) }}'
+    tox_env: >
+      {{ tox_env |
+         default({}) |
+         combine({ item.key: (item.value | string).strip() }) }}
+  loop: >
+    {{ ((tox_environment | from_yaml | dict2items) +
+        (tox_constrain_env | dict2items)) }}
+  when:
+    - (item.value | string).strip()  # skip empty strings
 
 - name: show tox variables
   debug: var="{{ item }}"