pythonPackages.pymc3: fix build, init pythonPackages.fastprogress at 1.0.0

[risicle]

Motivation for this change

ZHF: #97479

This has to wait on both:

• getting Theano fixed and working again, either by pythonPackages.Theano: set NIX_ENFORCE_PURITY=0 for invocation of wrapped compiler #99516 or other means
• getting arviz building again: pythonPackages.arviz: 0.7.0 -> 0.10.0, fixing tests #99500

Includes new dependency fastprogress.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[risicle]

@ofborg build python37Packages.pymc3

[risicle]

This is a fun situation - the issues holding up this PR have been resolved, but in that time, the dependency tensorflow has been broken in master. So testing this PR is difficult. But the reason I actually want it merged is because I need to backport it to 20.09, where it will be able to actually fix pymc3. I promise.

So, seeing as pymc3 was previously broken anyway, I wonder if anyone would find it in their hearts to "just trust me".

[jonringer]

i think it's fine. it's still an improvement, just because tensorflow likes to die every other week shouldn't keep this from also being backported