KYIV, Ukraine — Moscow flexed its geopolitical muscles last week with the welding together of two pipes in southern Russia: the formal launch of construction on a new natural gas pipeline to southern Europe. However, it’s not clear how well that strategy will work as countries in Central and Eastern Europe that rely heavily on Russian gas begin to diversify their supplies. New alternative sources are pushing down global prices and raising serious questions about Gazprom and its long-term strategy. The energy landscape is changing even in Ukraine, the very symbol of energy dependence on Russia.