- update to 2.22:
* Added a ``satnum_str`` attribute, exposing the fact that the C++ now
stores the satellite number as a string; and check that ``satnum`` is
never greater than 339999.
* Fixed the units of the ``nddot`` attribute when the value is loaded
from an OMM record. (Since the TLE computation itself ignores this
attribute, this did not affect any satellite positions.)
* Enhanced the fallback Python version of ``twoline2rv()`` to verify
that TLE lines are ASCII, and added documentation using it to
double-check TLEs that might suffer from non-ASCII characters.
* If the user doesn’t set a satellite’s ``classification``, it now
defaults to ``'U'`` for ‘unclassified’.
* Added ``dump_satrec()`` to the ``sgp4.conveniences`` module.
* Fixed the ``Satrec`` attribute ``.error``, which was previously
building a nonsense integer from the wrong data in memory.
* Removed ``.whichconst`` from Python ``Satrec``, to help users avoid
writing code that will break when the C++ extension is available.