Perform basic sanity checking when reading hints files

The only test currently implemented is to ensure that any prospective
hint contains at least one item beyond the hint name.  This prevents
lines in a hint file consisting simply of e.g. "easy" being added to
the hint list and causing later processing to abort with an error.

Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>

britney.py

@@ -813,6 +813,9 @@ class Britney(object):
                     break
                 elif l[0] not in self.HINTS[who]:
                     continue
+                elif len(l) == 1:
+                    # All current hints require at least one argument
+                    self.__log("Malformed hint found in %s: '%s'" % (filename, line), type="W")
                 elif l[0] in ["approve", "block", "block-all", "block-udeb", "unblock", "unblock-udeb", "force", "urgent", "remove"]:
                     for package in l[1:]:
                         hints.add_hint('%s %s' % (l[0], package), who)