Hello google travelers who have landed here!
I also got this error with conda when installing pytorch-cpu and torchvision-cpu.
Conda is limited to installing versions that are available as packages via the configured channels. You can see which versions are available by using conda search <package>.
pytorch-cpu and torchvision-cpu are packages available only via the conda-forge channel and only a limited selection of old versions for these packages is available there.
What you should do instead is to add the pytorch channel by using
# conda config --add channels pytorch
and install a suitable pytorch/torchvision package available through that channel. It’s an official channel that is kept up-to-date, and also offers a long list of older versions of pytorch and related packages, prepared for various versions of python.