give a less ambiguous warning for sniff failure
tree0d439651bcf3afd596aa68f12885bdfd1f9e2dfe
drwxr-xr-x - .github
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-rw-r--r-- 29111 CHANGELOG.md
-rw-r--r-- 630 CONTRIBUTING.md
-rw-r--r-- 36929 Cargo.lock
-rw-r--r-- 1794 Cargo.toml
-rw-r--r-- 40 Cross.toml
-rw-r--r-- 1221 LICENSE
-rw-r--r-- 5241 README.md
drwxr-xr-x - benchmarks
-rw-r--r-- 1581 build.rs
-rw-r--r-- 303 rustfmt.toml
drwxr-xr-x - scripts
drwxr-xr-x - src
drwxr-xr-x - tests