Get the string from the output that was generated
by a call to bin bin_cmd. If was not successful
print the error and exit. If quiet is false
also print any warning detected (stderr output).
Get a slug version of the text compatible with
a tag name to be published in a docker registry, with
only number, letters, the symbol “-” or the symbol “.”,
and no more than 63 characters long, all in lowercase.
Get the regex value expressed in &str, or exit if the filter
passed doesn’t star with “regex=” or “regex!=” prefixes.
When expression has “=” the bool is true, when is “!=”
the bool is false.
If the option passed is None, this method returns None as well.