change language to reflect the fact that conflicting namespaces are permitted, if discouraged

src/Bundle.js

@@ -220,8 +220,7 @@ export default class Bundle {
 						const exportAllModule = this.moduleById.get( id );
 						keys( exportAllModule.exportsAll ).forEach( name => {
 							if ( name in module.exportsAll ) {
-								this.onwarn( `A module cannot have multiple exports with the same name ('${name}')` +
-									` from ${module.exportsAll[ name ] } and ${exportAllModule.exportsAll[ name ]}` );
+								this.onwarn( `Conflicting namespaces: ${module.id} re-exports '${name}' from both ${module.exportsAll[ name ]} (will be ignored) and ${exportAllModule.exportsAll[ name ]}.` );
 							}
 							module.exportsAll[ name ] = exportAllModule.exportsAll[ name ];
 						});

test/function/double-named-export-from/_config.js

@@ -1,15 +1,15 @@
 const path = require('path');
 const assert = require( 'assert' );
 
-function normalize( file ) {
+function normalize ( file ) {
 	return path.resolve( __dirname, file ).split( '\\' ).join( '/' );
 }
 
 module.exports = {
 	description: 'throws on duplicate export * from',
-	warnings(warnings) {
-		assert.equal( warnings[0], `A module cannot have multiple exports with the same name ('foo')` +
-			` from ${normalize( 'foo.js' )} and ${normalize( 'deep.js' )}` );
-		assert.equal( warnings.length, 1 );
+	warnings ( warnings ) {
+		assert.deepEqual( warnings, [
+			`Conflicting namespaces: ${normalize('main.js')} re-exports 'foo' from both ${normalize('foo.js')} (will be ignored) and ${normalize('deep.js')}.`
+		]);
 	}
 };