Prevent compile error when the result of repr() is assigned to a "unicode" LHS with language_level=3.
Closes https://github.com/cython/cython/issues/3736

exec() did not allow recent Python syntax features in Py3.8+ due to https://bugs.python.org/issue35975
Closes https://github.com/cython/cython/issues/3695

Re-add "c_api_binop_methods" directive for backwards compatibility after reverting https://github.com/cython/cython/pull/3633 and force it to "False".
Closes #3688.

Closes https://github.com/cython/cython/issues/3674

Return statements inside of nested try-except statements lead to an incorrect control flow graph that did not take the outer 'finally' clauses into account.
Closes https://github.com/cython/cython/issues/3666

This avoids the METH_O function signature by default, since it does not match normal Python semantics.

* Fix unicode name handling of no-args functions when allowing keywords.

* Fix a crash when a keyword argument is passed to a function that does not allow them. Previously, the reported key name was not set and thus NULL.

* Extend "always_allow_keywords" test to cover some edge cases.
Some are commented out as they currently only work with the fastcall implementation.