support multi-line notes and notes with complex formatting

Change-Id: Iedfe043ef3a166b075871f55148468ccebe94ea6

releasenotes/notes/support-multi-line-notes-328853d8d596fd64.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    Support note entries that span multiple lines using
+    preformatted syntax in YAML by prefixing the
+    list entry with ``|``.
+
+    For example::
+
+      - |
+        This entry has two paragraphs.
+
+        This is the second.

reno/formatter.py

@@ -28,6 +28,18 @@ _SECTION_ORDER = [
 ]
 
 
+def _indent_for_list(text, prefix='  '):
+    """Indent some text to make it work as a list entry.
+
+    Indent all lines except the first with the prefix.
+    """
+    lines = text.splitlines()
+    return '\n'.join([lines[0]] + [
+        prefix + l
+        for l in lines[1:]
+    ]) + '\n'
+
+
 def format_report(reporoot, scanner_output, versions_to_include, title=None):
     report = []
     if title:
@@ -71,7 +83,7 @@ def format_report(reporoot, scanner_output, versions_to_include, title=None):
                 report.append('-' * len(section_title))
                 report.append('')
                 for n in notes:
-                    report.append('- %s' % n)
+                    report.append('- %s' % _indent_for_list(n))
                 report.append('')
 
     return '\n'.join(report)