Don't build failure_derive

Author: ecstatic-morse

Cargo.toml

@@ -24,9 +24,13 @@ members = [
 proc-macro = true
 
 [dependencies]
-failure = "0.1.5"
 proc-macro2 = "1.0"
 quote = "1.0"
 enum-utils-from-str = { path = "from-str", version = "0.1.0" }
 serde_derive_internals = "0.24.1"
 syn = { version = "1.0", features = ["extra-traits"] }
+
+[dependencies.failure]
+version = "0.1.5"
+default-features = false
+features = ["std"]