in app/build.gradle file
buildTypes.each {
it.buildConfigField 'String', 'OPEN_WEATHER_MAP_API_KEY', MyOpenWeatherMapApiKey
needs to be corrected.
The MyOpenWeatherMapApiKey should be specified within '"key"' i.e, '"actual_key"'
This may not not be an issue, but needs comment or correction in the source code else the buildconfig.Java will throw an error