The antlib of antunit defines xmlns:au="antlib:org.apache.ant.antunit
and uses it to define several elements in a sequence. It should use the ant:current namespace instead.

But the ant manual does not allow such pegging, but asks for use of the ant:current namespace.

https://ant.apache.org/manual/Types/antlib.html#currentnamespace

Quote:

"Definitions defined in antlibs may be used in antlibs. However, the namespace that definitions are placed in are dependent on the <typedef> that uses the antlib. To deal with this problem, the definitions are placed in the namespace URI ant:current for the duration of the antlib execution."