quspin v0.3.4: incompatiblity with numba=0.49.0

Hello, I encounter a strange bug after updating to the latest version 0.3.4 via my miniconda distro on a cluster, as well as a proper anaconda distro on my PC. So I uninstalled all my miniconda distros and reinstalled it completely fresh. The only command I entered before the error messages below, was conda install -c weinbe58 omp quspin.

As you can see below, the first error about numba can be fixed by manually importing it. However, it throws a different error about a missing cython function after importing:

Python 3.7.6 (default, Jan  8 2020, 19:59:22)
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import quspin
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "~/miniconda3/lib/python3.7/site-packages/quspin/__init__.py", line 3, in <module>
    from . import operators
  File "~/miniconda3/lib/python3.7/site-packages/quspin/operators/__init__.py", line 54, in <module>
    from .quantum_operator_core import *
  File "~/miniconda3/lib/python3.7/site-packages/quspin/operators/quantum_operator_core.py", line 3, in <module>
    from ..basis import spin_basis_1d as _default_basis
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/__init__.py", line 118, in <module>
    from .basis_general import *
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/__init__.py", line 1, in <module>
    from .spin import spin_basis_general
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/spin.py", line 1, in <module>
    from .base_hcb import hcb_basis_general
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/base_hcb.py", line 1, in <module>
    from ._basis_general_core import hcb_basis_core_wrap
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/_basis_general_core/__init__.py", line 6, in <module>
    from .user_core import user_core_wrap
  File "quspin/basis/basis_general/_basis_general_core/user_core.pyx", line 6, in init quspin.basis.basis_general._basis_general_core.user_core
ModuleNotFoundError: No module named 'numba.ccallback'
>>> import numba
>>> import quspin
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "~/miniconda3/lib/python3.7/site-packages/quspin/__init__.py", line 3, in <module>
    from . import operators
  File "~/miniconda3/lib/python3.7/site-packages/quspin/operators/__init__.py", line 54, in <module>
    from .quantum_operator_core import *
  File "~/miniconda3/lib/python3.7/site-packages/quspin/operators/quantum_operator_core.py", line 3, in <module>
    from ..basis import spin_basis_1d as _default_basis
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/__init__.py", line 118, in <module>
    from .basis_general import *
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/__init__.py", line 1, in <module>
    from .spin import spin_basis_general
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/spin.py", line 1, in <module>
    from .base_hcb import hcb_basis_general
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/base_hcb.py", line 1, in <module>
    from ._basis_general_core import hcb_basis_core_wrap
  File "~/miniconda3/lib/python3.7/site-packages/quspin/basis/basis_general/_basis_general_core/__init__.py", line 6, in <module>
    from .user_core import user_core_wrap
  File "quspin/basis/basis_general/_basis_general_core/source/general_basis_core.pyx", line 210, in init quspin.basis.basis_general._basis_general_core.user_core
AttributeError: type object 'quspin.basis.basis_general._basis_general_core.use' has no attribute '__reduce_cython__'

This missing cython function cannot be fixed by importing cython.

[weinbe58]

This should work:

try:
    from numba.ccallback import CFunc
except ModuleNotFoundError:
    from numba.core.ccallback import CFunc

[mgbukov]

I am re-opening this; we should resolve the numba compatibility or others will bump into the same problem.