Save abstract into a cache attribute. Fixes ietf-tools#587

 - Legacy-Id: 2849

Author: emiliosanchez

ietf/utils/draft.py

@@ -299,7 +299,8 @@ def get_abstract(self):
                     break
                 identation = new_identation
                 abstract.append(line)
-        return '\n'.join(abstract)
+        self._abstract = '\n'.join(abstract)
+        return self._abstract
 
 
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