Configurable loggers

loggers.jl

module Logging
    abstract Logger
    type DefaultLogger <: Logger
        stream::IO
        color::Symbol
        DefaultLogger() = new(STDERR, :blue)
        DefaultLogger(color::Symbol) = new(STDERR, color)
    end

    fatal(l::Logger, msg) = print_with_color(l.color, l.stream, "FATAL:", chomp(string(msg)), "\n")
    function fatal(msg...)
        m = current_module()
        l = if isconst(m, :logger) && isa(eval(:($m.logger)), Logger)
                eval(:($m.logger))
            else
                warn("Logger is not configured. Using default configuration.")
                Logging.DefaultLogger()
            end
        fatal(l, msg...)
    end
    export fatal, Logger
end

module A
    using Logging
    fatal("aaa")
end

module B
    using Logging
    const logger = Logging.DefaultLogger(:red)
    fatal("bbb")
    fatal(Logging.DefaultLogger(:yellow), "bbb")
end

module C
    using Logging
    const logger = 1
    fatal("aaa")
end