[PATCH 03 of 18 "] verify: document the `err` method

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at octobus.net>
# Date 1551867916 -3600
#      Wed Mar 06 11:25:16 2019 +0100
# Node ID 0124906dffd713a436215ab35ae56fd55b8ac77f
# Parent  0f480192d01335682e03e3c0793e7d380deb4bbe
# EXP-Topic verify
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 0124906dffd7
verify: document the `err` method

Simple method get simple documentation.

diff --git a/mercurial/verify.py b/mercurial/verify.py
--- a/mercurial/verify.py
+++ b/mercurial/verify.py
@@ -57,6 +57,7 @@ class verifier(object):
         self.warnings += 1
 
     def err(self, linkrev, msg, filename=None):
+        """record a "error" level issue"""
         if linkrev is not None:
             self.badrevs.add(linkrev)
             linkrev = "%d" % linkrev