Fix type assumption in Faraday::Error (#1630)

Following #1627, we began to assume that the parameter passed to `Faraday::Error#new` could only be either and `Exception` or a `Hash`.

As demonstrated in #1629, it turns out in the real world we're also passing `Faraday::Env` instances when building errors, which also respond to `each_key` and `[]` too.

Author: iMacTia

lib/faraday/error.rb

@@ -81,7 +81,7 @@ def exc_msg_and_response!(exc, response = nil)
     def exc_msg_and_response(exc, response = nil)
       if exc.is_a?(Exception)
         [exc, exc.message, response]
-      elsif exc.is_a?(Hash)
+      elsif exc.is_a?(Hash) || exc.is_a?(Faraday::Env)
         http_status = exc.fetch(:status)
 
         request = exc.fetch(:request, nil)