dashmap 4.0.0-rc5

# rustc version
rustc 1.45.0-nightly (5fd2f06e9 2020-05-31)# docs.rs version
docsrs 0.6.0 (9bd032f 2020-05-31)# build log
[INFO] running `Command { std: "docker" "create" "-v" "/home/cratesfyi/workspace/builds/dashmap-4.0.0-rc5/target:/opt/rustwide/target:rw,Z" "-v" "/home/cratesfyi/workspace/builds/dashmap-4.0.0-rc5/source:/opt/rustwide/workdir:ro,Z" "-v" "/home/cratesfyi/workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/home/cratesfyi/workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=1001" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "RUSTFLAGS=" "-e" "RUSTDOCFLAGS=-Z unstable-options --resource-suffix -20200531-1.45.0-nightly-5fd2f06e9 --static-root-path / --cap-lints warn --extern-html-root-url once_cell=https://docs.rs/once_cell/1.4.0" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "3221225472" "--cpus" "2" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+nightly" "doc" "--lib" "--no-deps" "-j2" "--features" "serde", kill_on_drop: false }`
[INFO] [stdout] cca3ec35f152f0590065ecbe29b147ced95b02b72cd75aa8092bc228fcebefeb
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "cca3ec35f152f0590065ecbe29b147ced95b02b72cd75aa8092bc228fcebefeb", kill_on_drop: false }`
[INFO] [stderr] sudo: setrlimit(RLIMIT_CORE): Operation not permitted
[INFO] [stderr]    Compiling serde v1.0.111
[INFO] [stderr]     Checking once_cell v1.4.0
[INFO] [stderr]  Documenting dashmap v4.0.0-rc5 (/opt/rustwide/workdir)
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 9.58s
[INFO] running `Command { std: "docker" "inspect" "cca3ec35f152f0590065ecbe29b147ced95b02b72cd75aa8092bc228fcebefeb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cca3ec35f152f0590065ecbe29b147ced95b02b72cd75aa8092bc228fcebefeb", kill_on_drop: false }`
[INFO] [stdout] cca3ec35f152f0590065ecbe29b147ced95b02b72cd75aa8092bc228fcebefeb