[Cython] Cython 0.28.1 released

[Stefan Behnel]

Hi all,

thanks to your excellent bug reports, here is a bug fix release for the
recent 0.28.

https://pypi.python.org/pypi/Cython/0.28.1

Changelog:
https://github.com/cython/cython/blob/0.28.1/CHANGES.rst

Bugs fixed for this release:

* ``PyFrozenSet_New()`` was accidentally used in PyPy where it is missing
  from the C-API.

* Assignment between some C++ templated types were incorrectly rejected
  when the templates mix ``const`` with ``ctypedef``.
  (Github issue #2148)

* Undeclared C++ no-args constructors in subclasses could make the
  compilation fail if the base class constructor was declared without
  ``nogil``.  (Github issue #2157)

* Bytes %-formatting inferred ``basestring`` (bytes or unicode) as result
  type in some cases where ``bytes`` would have been safe to infer.
  (Github issue #2153)

* ``None`` was accidentally disallowed as typed return value of
  ``dict.pop()``. (Github issue #2152)


Have fun,

Stefan