Add a yamllint check for workflows

.github/workflows/build.yml

@@ -123,6 +123,7 @@ jobs:
           - flake8
           - check-manifest
           - check-python-versions
+          - yamllint
 
     steps:
       - name: Git clone

.yamllint

@@ -0,0 +1,6 @@
+extends: default
+
+rules:
+  document-start: disable
+  line-length: disable
+  truthy: {check-keys: false}

MANIFEST.in

@@ -9,6 +9,7 @@ include Makefile
 include install-rpm.sh
 include .project
 include .pydevproject
+include .yamllint
 
 recursive-include cgi-bin               \
     *.css                               \

tox.ini

@@ -37,3 +37,8 @@ commands = check-manifest {posargs}
 deps = check-python-versions
 skip_install = true
 commands = check-python-versions {posargs}
+
+[testenv:yamllint]
+deps = yamllint
+skip_install = true
+commands = yamllint {posargs} -s .github/workflows/