Compiling hex-literal v0.1.4 = error: proc-macro derive panicked (#3134)

[iammelea]

~/akropolis/node$ ./scripts/build.sh
Building webassembly binary in runtime/wasm...
   Compiling proc-macro2 v0.4.30
   Compiling unicode-xid v0.1.0
   Compiling syn v0.15.35
   Compiling serde v1.0.92
   Compiling arrayvec v0.4.10
   Compiling semver-parser v0.7.0
   Compiling byteorder v1.3.2
   Compiling nodrop v0.1.13
   Compiling crunchy v0.2.2
   Compiling static_assertions v0.2.5
   Compiling rustc-hex v2.0.1
   Compiling autocfg v0.1.4
   Compiling hash-db v0.12.3
   Compiling constant_time_eq v0.1.3
   Compiling proc-macro-hack-impl v0.4.1
   Compiling integer-sqrt v0.1.2
   Compiling bitmask v0.5.0
   Compiling semver v0.9.0
   Compiling fixed-hash v0.3.2
   Compiling proc-macro-hack v0.4.1
   Compiling num-traits v0.2.8
   Compiling hex-literal-impl v0.1.2
   Compiling rustc_version v0.2.3
   Compiling blake2-rfc v0.2.18
   Compiling uint v0.7.1
   Compiling hash256-std-hasher v0.12.3
   Compiling hex-literal v0.1.4
error: proc-macro derive panicked
  --> /home/akropolis/.cargo/registry/src/github.amrom.workers.dev-1ecc6299db9ec823/hex-literal-0.1.4/src/lib.rs:38:1
   |
38 | / proc_macro_expr_decl! {
39 | |     /// Macro for converting hex string to byte array at compile time
40 | |     hex! => hex_impl
41 | | }
   | |_^
   |
   = help: message: assertion failed: `(left == right)`
             left: `Some("#[allow(unused,")`,
            right: `Some("#[allow(unused")`
   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to previous error

error: Could not compile `hex-literal`.
warning: build failed, waiting for other jobs to finish...
error: build failed

the solution
paritytech/substrate#3141