Re-enable rustfmt on CI

[gnzlbg]

No description provided.

[rust-highfive]

@gnzlbg: no appropriate reviewer found, use r? to override

[gnzlbg]

@bors: r+

[bors]

📌 Commit b7770f1 has been approved by gnzlbg

[bors]

⌛ Testing commit b7770f1 with merge c808230...

[bors]

💔 Test failed - checks-travis

[mati865]

Spurious:

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated

[gnzlbg]

This is done as part of #1376 .