Merge pull request
#1414 from minrk/var_expand
ignore errors in shell.var_expand
If an error is raised in the formatter, leave it untransformed. This means that var_expand("$foo") will return "$foo" if foo is undefined, but more importantly it will not raise when var_expand is used on literal code that doesn't expect to be expanded (e.g. %prun arguments).
closes
#1412
