Fixes [Issue #367](#367) where expired refresh tokens were not cleared, preventing re-authorization.

Author: josephquigley

Sources/Flows/OAuth2.swift

@@ -391,6 +391,9 @@ open class OAuth2: OAuth2Base {
 					callback(json, nil)
 				}
 				catch let error {
+					// Fixes [Issue #367](https://github.com/p2/OAuth2/issues/367)
+					// Refresh token needs to be cleared out upon error, otherwise re-authorizing will not ocurr because the library thinks it has a valid refresh token and tries to fetch a new access token with an expired refresh token.
+					self.clientConfig.refreshToken = nil
 					self.logger?.debug("OAuth2", msg: "Error refreshing access token: \(error)")
 					callback(nil, error.asOAuth2Error)
 				}

Sources/Flows/OAuth2PasswordGrant.swift

@@ -68,6 +68,7 @@ open class OAuth2PasswordGrant: OAuth2 {
 
 	/// Properties used to handle the native controller.
 	open lazy var customAuthorizer: OAuth2CustomAuthorizerUI = OAuth2CustomAuthorizer()
+	
 	/**
 	If credentials are unknown when trying to authorize, the delegate will be asked a login controller to present.