Add enum34 to empty packages

Author: BastianZim

src/maintainer/knowledge_base.rst

@@ -924,6 +924,8 @@ Currently available packages:
 +=============+===================+==============+
 | dataclasses | python >=3.6,<3.7 | python >=3.7 |
 +-------------+-------------------+--------------+
+| enum34      | python =2.7       | python >=3.4 |
++-------------+-------------------+--------------+
 | typing      |                   | python >=3   |
 +-------------+-------------------+--------------+