I faced this issue on my mac after updating conda. Solution was to run conda mini installer on top of existing conda setup.
$ curl https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh -o ~/miniconda3.sh
$ bash ~/miniconda3.sh -bfp ~/miniconda3
On linux, you can use:
$ curl https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -o ~/miniconda3.sh
$ bash ~/miniconda3.sh -bfp ~/miniconda3
For other versions, you can go to https://repo.continuum.io/miniconda/
For details check: https://github.com/conda/conda/issues/1364