Error: [Cabal-7107] Could not resolve dependencies:

[besiwims]

wims@wims-Precision-7530:~/plutus-pioneer-program/code/Week02$ cabal repl
Resolving dependencies...
Error: [Cabal-7107]
Could not resolve dependencies:
[__0] next goal: byron-spec-chain (user goal)
[__0] rejecting: byron-spec-chain; 0.1.1.2, 0.1.1.1 (constraint from user target requires ==0.1.0.0)
[__0] trying: byron-spec-chain-0.1.0.0
[__1] next goal: base (dependency of byron-spec-chain)
[__1] rejecting: base-4.17.2.1/installed-4.17.2.1 (conflict: byron-spec-chain => base>=4.12 && <4.15)
[__1] skipping: base; 4.17.0.0, 4.16.4.0, 4.16.3.0, 4.16.2.0, 4.16.1.0, 4.16.0.0, 4.15.1.0, 4.15.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=4.12 && <4.15' from 'byron-spec-chain')
[__1] rejecting: base; 4.14.3.0, 4.14.2.0, 4.14.1.0, 4.14.0.0, 4.13.0.0, 4.12.0.0, 4.11.1.0, 4.11.0.0, 4.10.1.0, 4.10.0.0, 4.9.1.0, 4.9.0.0, 4.8.2.0, 4.8.1.0, 4.8.0.0, 4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (constraint from non-reinstallable package requires installed instance)
[__1] fail (backjumping, conflict set: base, byron-spec-chain)
After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, byron-spec-chain

This was working fine before and now we need to know what changed?