Empty log analysis for PR 52602

[scottmcm]

Bot comment: rust-lang/rust#52602 (comment)

Travis job: https://travis-ci.org/rust-lang/rust/builds/406742818?utm_source=github_status&utm_medium=notification

Expected error

Some part of this:

[01:19:59] command did not execute successfully: "/checkout/obj/build/bootstrap/debug/rustdoc" "--test" "/checkout/src/doc/unstable-book/src/language-features/catch-expr.md" "--test-args" ""
[01:19:59] expected success, got: exit code: 101
[01:19:59] 
[01:19:59] stdout ----
[01:19:59] 
[01:19:59] running 1 test
[01:19:59] test /checkout/src/doc/unstable-book/src/language-features/catch-expr.md - catch_expr (line 12) ... FAILED
[01:19:59] 
[01:19:59] failures:
[01:19:59] 
[01:19:59] ---- /checkout/src/doc/unstable-book/src/language-features/catch-expr.md - catch_expr (line 12) stdout ----
[01:19:59] error: expected expression, found reserved keyword `do`
[01:19:59]  --> /checkout/src/doc/unstable-book/src/language-features/catch-expr.md:17:42
[01:19:59]   |
[01:19:59] 7 | let result: Result<i32, ParseIntError> = do catch {
[01:19:59]   |                                          ^^ expected expression
[01:19:59] 
[01:19:59] thread '/checkout/src/doc/unstable-book/src/language-features/catch-expr.md - catch_expr (line 12)' panicked at 'couldn't compile the test', librustdoc/test.rs:327:17
[01:19:59] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:19:59] 
[01:19:59] 
[01:19:59] failures:
[01:19:59]     /checkout/src/doc/unstable-book/src/language-features/catch-expr.md - catch_expr (line 12)
[01:19:59] 
[01:19:59] test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
[01:19:59] 
[01:19:59] 
[01:19:59] stderr ----
[01:19:59] 
[01:19:59] 
[01:19:59] 
[01:19:59] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:19:59] Build completed unsuccessfully in 0:34:00
[01:19:59] Makefile:58: recipe for target 'check' failed
[01:19:59] make: *** [check] Error 1

[tbu-]

Empty analysis: rust-lang/rust#126391 (comment)

Would be better to not show "Click to see the possible cause of the failure (guessed by this bot)" but rather "couldn't guess the possible cause of the failure".