bugdown: Disable linebreaks from two spaces at end-of-line.

Arguably the nl2br extension should be doing this for us.  Given that
we're using nl2br, the "two spaces at the end of a line makes a line
break" rule doesn't make any sense (since every newline leads to a
linebreak), so we disable it.

(imported from commit 5ffa2ac8a825642ad31e085c532091e076665710)

zerver/lib/bugdown/__init__.py

@@ -613,7 +613,7 @@ class Bugdown(markdown.Extension):
         for k in ('image_link', 'image_reference', 'automail',
                   'autolink', 'link', 'reference', 'short_reference',
                   'escape', 'strong_em', 'emphasis', 'emphasis2',
-                  'strong'):
+                  'linebreak', 'linebreak2', 'strong'):
             del md.inlinePatterns[k]
 
         md.preprocessors.add("custom_text_notifications", AlertWordsNotificationProcessor(md), "_end")

zerver/tests.py

@@ -3196,6 +3196,15 @@ xxxxxxx</strong></p>\n<p>xxxxxxx xxxxx xxxx xxxxx:<br>\n<code>xxxxxx</code>: xxx
 
         self.assertEqual(converted, '<p>Look at the new dropbox logo: <a href="https://www.dropbox.com/static/images/home_logo.png" target="_blank" title="https://www.dropbox.com/static/images/home_logo.png">https://www.dropbox.com/static/images/home_logo.png</a></p>\n<div class="message_inline_image"><a href="https://www.dropbox.com/static/images/home_logo.png" target="_blank" title="https://www.dropbox.com/static/images/home_logo.png"><img src="https://www.dropbox.com/static/images/home_logo.png"></a></div>')
 
+    def test_nl2br(self):
+        msg = 'test\nbar'
+        converted = bugdown_convert(msg)
+        self.assertEqual(converted, '<p>test<br>\nbar</p>')
+
+        msg = 'test  '
+        converted = bugdown_convert(msg)
+        self.assertEqual(converted, '<p>test  </p>')
+
     def test_inline_interesting_links(self):
         def make_link(url):
             return '<a href="%s" target="_blank" title="%s">%s</a>' % (url, url, url)