Does exist anything like the built-in-mesh UnitCircle now? Because this one does not seems to work anymore. Thanks.
Non-trivial mesh generation has been moved in the mshr package:
mshr
https://bitbucket.org/benjamik/mshr
mshr doesn't appear to have a UnitCircleMesh class, but does have the necessary tools to create a unit circle mesh.
UnitCircleMesh