Drop the Cython version check from setup.py

This avoids the dependency on the pkg_resources module, which has long been deprecated and is no longer shipped with current versions of setuptools.

Author: musicinmybrain

setup.py

@@ -188,8 +188,6 @@ def finalize_options(self):
                         need_cythonize = True
 
         if need_cythonize:
-            import pkg_resources
-
             # Double check Cython presence in case setup_requires
             # didn't go into effect (most likely because someone
             # imported Cython before setup_requires injected the
@@ -201,13 +199,6 @@ def finalize_options(self):
                     'please install {} to compile asyncpg from source'.format(
                         CYTHON_DEPENDENCY))
 
-            cython_dep = pkg_resources.Requirement.parse(CYTHON_DEPENDENCY)
-            if Cython.__version__ not in cython_dep:
-                raise RuntimeError(
-                    'asyncpg requires {}, got Cython=={}'.format(
-                        CYTHON_DEPENDENCY, Cython.__version__
-                    ))
-
             from Cython.Build import cythonize
 
             directives = {