build with cython3, WIP (Closes: #1056874)

debian/clean

+.eggs/README.txt

debian/control

@@ -6,7 +6,7 @@ Testsuite: autopkgtest-pkg-python
 Priority: optional
 Build-Depends: debhelper-compat (= 13),
                dh-sequence-python3,
-               cython3-legacy,
+               cython3,
                python3-all-dev,
                python3-setuptools,
                python3-ruamel.yaml,

debian/patches/cython3.patch

+--- a/srsly/msgpack/_unpacker.pyx
++++ b/srsly/msgpack/_unpacker.pyx
+@@ -10,7 +10,6 @@
+ from libc.stdlib cimport *
+ from libc.string cimport *
+ from libc.limits cimport *
+-ctypedef unsigned long long uint64_t
+ 
+ from .exceptions import (
+     BufferFull,
+--- a/setup.cfg
++++ b/setup.cfg
+@@ -31,7 +31,7 @@
+ include_package_data = true
+ python_requires = >=3.6
+ setup_requires =
+-    cython>=0.29.1,<0.30.0
++    cython>=0.29.1
+ install_requires =
+     catalogue>=2.0.3,<2.1.0
+ 

debian/patches/series

 unittest-mock.patch
+cython3.patch