nrpe.Check._locate_cmd incorrectly parses check_cmd

[Alvaro Uria]

if check_cmd is of the type:
check_http -I 127.0.0.1 -p 8193 -u / -s 'OpenStack Exporter'

_locate_cmd will parse it as:
/usr/lib/nagios/plugins/check_http -I 127.0.0.1 -p 8193 -u / -s OpenStack Exporter

We want to preserve quotes when they exist, so as to get:
/usr/lib/nagios/plugins/check_http -I 127.0.0.1 -p 8193 -u / -s 'OpenStack Exporter'

Fix is:

- command += " " + " ".join(parts[1:])
+ command += " " + " ".join(shlex.quote(part) for part in parts[1:])

[Alvaro Uria (aluria)]

PR at https://github.com/juju/charm-helpers/pull/325

[Alvaro Uria (aluria)]

shlex.quote is not supported in py2. A different approach will be needed.

[Alvaro Uria (aluria)]

Possibly replicate the shlex.quote code from py3 in the nrpe.py module:
"""
_find_unsafe = re.compile(r'[^\w@%+=:,./-]', re.ASCII).search

def quote(s):
    """Return a shell-escaped version of the string *s*."""
    if not s:
        return "''"
    if _find_unsafe(s) is None:
        return s

    # use single quotes, and put single quotes into double quotes
    # the string $'b is then quoted as '$'"'"'b'
    return "'" + s.replace("'", "'\"'\"'") + "'"
"""