More detailed error reporting if key derivation fails

ChangeLog.txt

@@ -7,6 +7,7 @@ Fixed bugs:
 Improvements:
 * Allow building with -DCRYFS_UPDATE_CHECKS=off, which will create an executable with disabled update checks (the alternative to disable them in the environment also still works).
 * Automatically disable update checks when running in noninteractive mode.
+* More detailed error reporting if key derivation fails
 
 Compatibility:
 * Compatible with libcurl version >= 7.50.0, and <= 7.21.6 (tested down to 7.19.0)

src/cpp-utils/crypto/kdf/Scrypt.cpp

@@ -28,7 +28,7 @@ namespace cpputils {
                                       _config.N(), _config.r(), _config.p(),
                                       static_cast<uint8_t*>(destination), size);
         if (errorcode != 0) {
-            throw std::runtime_error("Error running scrypt key derivation.");
+            throw std::runtime_error("Error running scrypt key derivation. Error code: "+std::to_string(errorcode));
         }
     }