Allow user to make yamllint rule mandatory

Related: #1538

.ansible-lint

@@ -34,7 +34,9 @@ skip_list:
 # mentioned in the enable_list:
 enable_list:
   - no-same-owner
-
+  # add yaml here if you want to avoid ignoring yaml checks when yamllint
+  # library is missing. Normally its absence just skips using that rule.
+  - yaml
 # Report only a subset of tags and fully ignore any others
 # tags:
 #   - var-spacing

docs/requirements.in

@@ -4,3 +4,4 @@ pipdeptree
 Sphinx
 sphinx_ansible_theme
 sphinxcontrib-programoutput2>=2.0a1
+yamllint

docs/requirements.txt

@@ -5,9 +5,9 @@
 #    pip-compile --no-annotate --output-file=docs/requirements.txt docs/requirements.in setup.py
 #
 alabaster==0.7.12
-ansible-base==2.10.7
+ansible-base==2.10.8
 attrs==20.3.0
-babel==2.9.0
+babel==2.9.1
 bracex==2.1.1
 certifi==2020.12.5
 cffi==1.14.5
@@ -23,8 +23,9 @@ jinja2==2.11.3
 markdown-it-py==0.6.2
 markupsafe==1.1.1
 mdit-py-plugins==0.2.6
-myst-parser==0.13.5
+myst-parser==0.13.7
 packaging==20.9
+pathspec==0.8.1
 pipdeptree==2.0.0
 pycparser==2.20
 pygments==2.8.1
@@ -34,13 +35,13 @@ pyyaml==5.4.1
 requests==2.25.1
 rich==10.1.0
 ruamel.yaml.clib==0.2.2
-ruamel.yaml==0.17.2 ; python_version >= "3.7"
+ruamel.yaml==0.17.4 ; python_version >= "3.7"
 six==1.15.0
 snowballstemmer==2.1.0
 sphinx-ansible-theme==0.3.2
 sphinx-notfound-page==0.6
 sphinx-rtd-theme==0.5.2
-sphinx==3.5.3
+sphinx==3.5.4
 sphinxcontrib-applehelp==1.0.2
 sphinxcontrib-devhelp==1.0.2
 sphinxcontrib-htmlhelp==1.0.3
@@ -49,9 +50,10 @@ sphinxcontrib-programoutput2==2.0a1
 sphinxcontrib-qthelp==1.0.3
 sphinxcontrib-serializinghtml==1.1.4
 tenacity==7.0.0
-typing-extensions==3.7.4.3
+typing-extensions==3.10.0.0
 urllib3==1.26.4
 wcmatch==8.1.2
+yamllint==1.26.1
 
 # The following packages are considered to be unsafe in a requirements file:
 # pip

src/ansiblelint/rules/YamllintRule.py

@@ -3,6 +3,7 @@
 import sys
 from typing import TYPE_CHECKING, List
 
+from ansiblelint.config import options
 from ansiblelint.file_utils import Lintable
 from ansiblelint.rules import AnsibleLintRule
 from ansiblelint.skip_utils import get_rule_skips_from_line
@@ -17,7 +18,11 @@
     from yamllint.config import YamlLintConfig
     from yamllint.linter import run as run_yamllint
 except ImportError:
-    pass
+    # missing library is ignored unless yaml is exclitely added to enable_list
+    if 'yaml' in options.enable_list:
+        raise RuntimeError(
+            'Failed to load yamllint library and ansible-linted was configured to require it.'
+        )
 
 
 YAMLLINT_CONFIG = """
@@ -38,6 +43,10 @@
 Specific tag identifiers that are printed at the end of rule name,
 like 'trailing-spaces' or 'indentation' can also be be skipped, allowing
 you to have a more fine control.
+
+By default this rule is not used hwne yamllint library is missing. If you want
+to make its absence a runtime failure, please add 'yaml' to 'enable_list'
+inside the configuration file.
 """
 
 

test-requirements.txt

@@ -26,11 +26,11 @@ pytest==6.2.3
 pyyaml==5.4.1
 rich==10.1.0
 ruamel.yaml.clib==0.2.2
-ruamel.yaml==0.17.2 ; python_version >= "3.7"
+ruamel.yaml==0.17.4 ; python_version >= "3.7"
 six==1.15.0
 tenacity==7.0.0
 toml==0.10.2
-typing-extensions==3.7.4.3
+typing-extensions==3.10.0.0
 wcmatch==8.1.2
 
 # The following packages are considered to be unsafe in a requirements file: