Require log <= 0.3.8 for dev builds

Author: dhardy

Cargo.toml

@@ -29,7 +29,9 @@ libc = { version = "0.2", optional = true }
 winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "profileapi", "winnt"] }
 
 [dev-dependencies]
-log = "0.3.0"
+# log 0.3.9 is a wrapper around 0.4.0 which doesn't work with rustc 1.15
+# To keep our CI pin on 1.15 we require log <= 0.3.8.
+log = "0.3, <=0.3.8"
 
 [workspace]
 members = ["rand-derive"]