Add a non-reflowing formatter for help texts.

We want to be able to write pre-formatted command descriptions in our
plugins, where the text is not reflowed/re-wrapped by optparse when
printing (in response to the --help option).  E.g, because they have
code (Nagios config snippets) in them that don't fare well when being
reflowed.

We add a class NoReflowHelpFormatter to trh_nagioslib which can be
used for this.  It will still dedent the description text, so it
can be written indented in the plugin source, if wanted.

trh_nagioslib.py

@@ -13,6 +13,8 @@ import re
 import collections
 import netsnmp
 import subprocess
+import optparse
+import textwrap
 
 
 # Cache of mappings from short names to fully qualified names.
@@ -251,3 +253,21 @@ def nagios_report(statuses):
         message = "UNKNOWN: No status report\n"
 
     return max_level, message
+
+
+
+class NoReflowHelpFormatter(optparse.IndentedHelpFormatter):
+    """A HelpFormatter for optparse that does not re-wrap/reflow text.
+
+       Intended for command descriptions that are already properly
+       pre-formatted.
+    """
+    def format_description(self, description):
+        if not description:
+            return ""
+        desc_width = min(70, self.width - self.current_indent)
+        indent = " " * self.current_indent
+        summary,body = (description.strip().split("\n", 1) + [""])[:2]
+        body = textwrap.dedent(body)
+        description = summary + "\n" + body + "\n"
+        return description