Join string with char instead of &str to make clippy happy

1 job for require_contest_participation in 1 minute and 19 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #2344
test

00:01:19

 
Name Stage Failure
failed
test Test

For more information about this error, try `rustc --explain E0308`.
error: could not compile `medal`.

Caused by:
process didn't exit successfully: `rustc --crate-name medal src/main.rs --error-format=json --json=diagnostic-rendered-ansi --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --test --cfg 'feature="complete"' --cfg 'feature="debug"' --cfg 'feature="default"' --cfg 'feature="postgres"' --cfg 'feature="rusqlite"' --cfg 'feature="signup"' --cfg 'feature="strict"' --cfg 'feature="webbrowser"' -C metadata=8e636f3a8bc3afea -C extra-filename=-8e636f3a8bc3afea --out-dir /builds/bwinf/medal/target/debug/deps -C incremental=/builds/bwinf/medal/target/debug/incremental -L dependency=/builds/bwinf/medal/target/debug/deps --extern bcrypt=/builds/bwinf/medal/target/debug/deps/libbcrypt-c72853aadd70f106.rlib --extern csv=/builds/bwinf/medal/target/debug/deps/libcsv-4d0c2cd6bf4a1266.rlib --extern handlebars_iron=/builds/bwinf/medal/target/debug/deps/libhandlebars_iron-1e52bc5fd686f41f.rlib --extern iron=/builds/bwinf/medal/target/debug/deps/libiron-05e15d0c12b64d29.rlib --extern iron_sessionstorage=/builds/bwinf/medal/target/debug/deps/libiron_sessionstorage-61324ddd9396fc8f.rlib --extern linked_hash_map=/builds/bwinf/medal/target/debug/deps/liblinked_hash_map-707a45c481d370f0.rlib --extern mount=/builds/bwinf/medal/target/debug/deps/libmount-bcc1965b9b375d53.rlib --extern params=/builds/bwinf/medal/target/debug/deps/libparams-c9ae00dea2f5b2be.rlib --extern persistent=/builds/bwinf/medal/target/debug/deps/libpersistent-d7d4e14e10836cc5.rlib --extern postgres=/builds/bwinf/medal/target/debug/deps/libpostgres-b7d58501caccd609.rlib --extern rand=/builds/bwinf/medal/target/debug/deps/librand-51264a710b0c0bd9.rlib --extern reqwest=/builds/bwinf/medal/target/debug/deps/libreqwest-659205a32579db54.rlib --extern router=/builds/bwinf/medal/target/debug/deps/librouter-73605ba1aecee713.rlib --extern rusqlite=/builds/bwinf/medal/target/debug/deps/librusqlite-1f33722ba312eda5.rlib --extern serde=/builds/bwinf/medal/target/debug/deps/libserde-653a77ab1a9783e3.rlib --extern serde_derive=/builds/bwinf/medal/target/debug/deps/libserde_derive-2950beb942d77638.so --extern serde_json=/builds/bwinf/medal/target/debug/deps/libserde_json-87c856fa3134b7ba.rlib --extern serde_yaml=/builds/bwinf/medal/target/debug/deps/libserde_yaml-e657b7b3965c308d.rlib --extern sha2=/builds/bwinf/medal/target/debug/deps/libsha2-9ace23018e9543f0.rlib --extern staticfile=/builds/bwinf/medal/target/debug/deps/libstaticfile-19181edb518a7b06.rlib --extern structopt=/builds/bwinf/medal/target/debug/deps/libstructopt-1b68c1e28be68b52.rlib --extern time=/builds/bwinf/medal/target/debug/deps/libtime-70843a2482820132.rlib --extern urlencoded=/builds/bwinf/medal/target/debug/deps/liburlencoded-95922dedca7261ce.rlib --extern webbrowser=/builds/bwinf/medal/target/debug/deps/libwebbrowser-ecebdc9e24e74fd7.rlib -L native=/builds/bwinf/medal/target/debug/build/ring-ccc3d484f3a409c5/out` (exit code: 1)
make: *** [Makefile:14: stricttest] Error 101
Cleaning up file based variables
ERROR: Job failed: exit code 1