Comment 1 for bug 1382108

This comes from p.rpc.dhcp.create_host_maps: the CannotCreateHostMap
exception contains the Unicode character for an arrow. It's more than a
bit rubbish that Twisted's AMP implementation doesn't cope with
non-ASCII errors, but we can work around it at least.

Fwiw:

    Command `omshell` returned non-zero exit status 0:#012> > > > not
    connected.#012> no open object.#012> no open object.#012> no open
    object.#012> no open object.#012> not connected.#012>

is an example of the error message that comes out of __str__() and
__unicode__() on ExternalProcessError. The #012 bit is probably meant to
be octal for newline, but I'm not sure what's introducing it (syslog
maybe?).