Fix thor deprecation warning

Author: marcqualie

Diff for: CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 
 
+## [Unreleased]
+
+### Fixed
+
+- Thor deprecation error no longer shows on CLI failure
+
+
+
 ## [0.3.0] - 2020-06-30
 
 ## Added

Diff for: lib/diffcrypt/cli.rb

@@ -38,6 +38,10 @@ def encryptor
       def ensure_file_exists(path)
         abort('[ERROR] File does not exist') unless File.exist?(path)
       end
+
+      def self.exit_on_failure?
+        true
+      end
     end
   end
 end