Escape backslashes for Sphinx, in OptBucket

This fixes the -m flag documentation for both the README.txt and
nosetests.1 manpage.

README.txt

@@ -216,8 +216,8 @@ Options
 -m=REGEX, --match=REGEX, --testmatch=REGEX
 
    Files, directories, function names, and class names that match this
-   regular expression are considered tests.  Default:
-   (?:\b|_)[Tt]est [NOSE_TESTMATCH]
+   regular expression are considered tests.  Default: (?:\b|_)[Tt]est
+   [NOSE_TESTMATCH]
 
 --tests=NAMES
 

nose/sphinx/pluginopts.py

@@ -157,6 +157,8 @@ def format_help(self):
         return self.doc.replace('%prog', self.prog).replace(':\n', '::\n')
 
     def add_option(self, *arg, **kw):
+        kw = {k: (v.replace('\\', '\\\\') if isinstance(v, str) else v)
+              for (k, v) in kw.items()}
         self.opts.append(Opt(*arg, **kw))
 
 

nosetests.1

@@ -236,7 +236,7 @@ Look for tests in this directory under Python 3.x. Functions the same as \(aqwhe
 .INDENT 0.0
 .TP
 .B \-m=REGEX, \-\-match=REGEX, \-\-testmatch=REGEX
-Files, directories, function names, and class names that match this regular expression are considered tests.  Default: (?:^|[b_./\-])[Tt]est [NOSE_TESTMATCH]
+Files, directories, function names, and class names that match this regular expression are considered tests.  Default: (?:\eb|_)[Tt]est [NOSE_TESTMATCH]
 .UNINDENT
 .INDENT 0.0
 .TP