Dependencies resolution fails with numba `0.49`. I do not know the root cause.
Here is the difference between the two versions.

```bash
$ conda search --info numba

numba 0.48.0 py38hb3f55d8_0
---------------------------
file name   : numba-0.48.0-py38hb3f55d8_0.tar.bz2
name        : numba
version     : 0.48.0
build       : py38hb3f55d8_0
build number: 0
size        : 3.4 MB
license     : BSD 2-clause
subdir      : linux-64
url         : https://conda.anaconda.org/conda-forge/linux-64/numba-0.48.0-py38hb3f55d8_0.tar.bz2
md5         : 580c5132d9f575462db40daf20201ff1
timestamp   : 2020-01-27 17:39:57 UTC
constraints :
  - tbb >=2018.0.5
  - python_abi * *_cp38
dependencies:
  - libgcc-ng >=7.3.0
  - libstdcxx-ng >=7.3.0
  - llvmlite >=0.31.0,<0.32.0a0
  - numpy >=1.14.6,<2.0a0
  - python >=3.8,<3.9.0a0
  - setuptools

numba 0.49.0 py36h0573a6f_0
---------------------------
file name   : numba-0.49.0-py36h0573a6f_0.conda
name        : numba
version     : 0.49.0
build       : py36h0573a6f_0
build number: 0
size        : 3.1 MB
license     : BSD 2-clause
subdir      : linux-64
url         : https://repo.anaconda.com/pkgs/main/linux-64/numba-0.49.0-py36h0573a6f_0.conda
md5         : cdbf81e0d643b5e90441ccf110b97a3d
timestamp   : 2020-04-17 17:08:20 UTC
constraints :
  - tbb >=2018.0.5
dependencies:
  - libgcc-ng >=7.3.0
  - libstdcxx-ng >=7.3.0
  - llvmlite >=0.32.0
  - llvmlite >=0.32.0,<0.33.0a0
  - numpy >=1.14.6,<2.0a0
  - python >=3.6,<3.7.0a0
  - setuptools
  - tbb >=2020.0
 ```