assert, called at ./Distribution/Client/ProjectPlanning.hs:281:5

Using current cabal at c2dfc3310b71193a491424dddb8c4ab868c55b6e built with GHC 8.0.2,
configuring for use with GHC ghc-8.2 branch at b3f7e9b54d9f36938effd265c84d5567b34c905b, with a brand new install.

Trying to build https://github.com/alanz/ghc-exactprint/tree/ghc-8.2

```
cabal new-configure --enable-tests -fdev --with-compiler=/opt/ghc/8.2.0.20170321/bin/ghc --allow-newer
```

results in

```
Resolving dependencies...
In order, the following would be built (use -v for more details):
- Diff-0.3.4 (lib) (requires build)
- StateVar-1.1.0.4 (lib) (requires build)
- ansi-terminal-0.6.2.3 (requires build)
- async-2.1.1 (lib) (requires build)
- base-compat-0.9.2 (lib) (requires build)
- base-orphans-0.5.4 (lib) (requires build)
- cabal-doctest-1 (lib) (requires build)
- call-stack-0.1.0 (lib) (requires build)
- extensible-exceptions-0.1.1.4 (requires download & build)
- ghc-paths-0.1.0.9 (requires build)
- hostname-1.0 (requires build)
- hsc2hs-0.68.1 (exe:hsc2hs) (requires build)
- hspec-discover-2.4.2 (lib) (requires build)
- mtl-2.2.1 (requires build)
- old-locale-1.0.0.7 (lib) (requires build)
- prelude-extras-0.4.0.3 (requires build)
- primitive-0.6.2.0 (lib) (requires build)
- semigroups-0.18.2 (lib) (requires build)
- setenv-0.1.1.3 (lib) (requires build)
- silently-1.2.5 (lib) (requires build)
- stringbuilder-0.5.0 (lib) (requires download & build)
- syb-0.7 (lib) (requires build)
- text-1.2.2.1 (lib) (requires build)
- transformers-compat-0.5.1.4 (lib) (requires build)
- unix-compat-0.4.3.1 (requires build)
- with-location-0.1.0 (lib) (requires download & build)
- ansi-wl-pprint-0.6.7.3 (requires build)
- HUnit-1.6.0.0 (lib) (requires download & build)
- code-page-0.1.3 (lib) (requires build)
- hspec-discover-2.4.2 (exe:hspec-discover) (requires build)
- regex-base-0.93.2 (requires build)
- tf-random-0.5 (lib) (requires build)
- xml-1.3.14 (requires build)
- hashable-1.2.5.0 (lib) (first run)
- tagged-0.8.5 (lib) (requires build)
- exceptions-0.8.3 (lib) (requires build)
- filemanip-0.3.6.3 (requires build)
- hspec-expectations-0.8.2 (lib) (requires build)
- doctest-0.11.1 (lib) (first run)
- regex-posix-0.95.2 (requires download & build)
- QuickCheck-2.9.2 (lib) (requires build)
- void-0.7.1 (lib) (requires build)
- distributive-0.5.2 (requires build)
- doctest-0.11.1 (test:doctests) (first run)
- doctest-0.11.1 (exe:doctest) (first run)
- test-framework-0.8.1.1 (requires download & build)
- quickcheck-io-0.1.4 (lib) (requires build)
- contravariant-1.4 (requires build)
- test-framework-quickcheck2-0.3.0.3 (requires download & build)
- test-framework-hunit-0.3.0.2 (requires download & build)
- hspec-core-2.4.2 (lib) (requires build)
Assertion failed
CallStack (from HasCallStack):
assert, called at ./Distribution/Client/ProjectPlanning.hs:281:5 in cabal-install-2.1.0.0-inplace:Distribution.Client.ProjectPlanning
```