This source package is Debian-native and has a debian/upstream/metadata file.
The Upstream MEtadata GAthered with YAml (UMEGAYA) project is an effort to collect meta-information about upstream projects from any source package. This file is in YAML format and it is used in to feed the data in the UltimateDebianDatabase. For example, it can contains the way the authors want their software be cited in publications and some bibliographic references about the software.
Please remove the debian/upstream/metadata file.