Washington Post: Exxon Mobil said that one of its pipelines leaked a few thousand barrels of Canadian heavy crude oil near Mayflower, Ark., prompting the evacuation of 22 homes and reinforcing concerns many critics have raised about the Keystone XL pipeline that is awaiting State Department approval. The pipeline breach took place late Friday, Exxon said, in the 20-inch diameter, 95,000-barrel-a-day Pegasus pipeline, which originates in Patoka, Ill., and carries crude oil to the Texas Gulf Coast, the countrys...