Throwing error when the configs fail JSON serialization (#114)

* Added error for JSON serialization errors

* Fix merge commit

---------

Co-authored-by: Pedro Cuenca <pedro@huggingface.co>

Author: pcuenca

Sources/Hub/Hub.swift

@@ -14,6 +14,7 @@ public extension Hub {
         case authorizationRequired
         case httpStatusCode(Int)
         case parse
+        case jsonSerialization(fileURL: URL, message: String)
         case unexpectedError
         case downloadError(String)
         case fileNotFound(String)
@@ -31,6 +32,8 @@ public extension Hub {
                 String(localized: "HTTP error with status code: \(code)")
             case .parse:
                 String(localized: "Failed to parse server response.")
+            case .jsonSerialization(_, let message):
+                return message
             case .unexpectedError:
                 String(localized: "An unexpected error occurred.")
             case let .downloadError(message):

Sources/Hub/HubApi.swift

@@ -268,7 +268,9 @@ public extension HubApi {
     /// `fileURL` is a complete local file path for the given model
     func configuration(fileURL: URL) throws -> Config {
         let data = try Data(contentsOf: fileURL)
-        let parsed = try JSONSerialization.bomPreservingJsonObject(with: data)
+        guard let parsed = try? JSONSerialization.bomPreservingJsonObject(with: data) else {
+            throw Hub.HubClientError.jsonSerialization(fileURL: fileURL, message: "JSON Serialization failed for \(fileURL). Please verify that you have set the HF_TOKEN environment variable.")
+        }
         guard let dictionary = parsed as? [NSString: Any] else { throw Hub.HubClientError.parse }
         return Config(dictionary)
     }