add workaround for npm-link'ed sane-topojson

Author: etpinard

tasks/util/constants.js

@@ -8,9 +8,20 @@ var pathToImageTest = path.join(pathToRoot, 'test/image');
 var pathToDist = path.join(pathToRoot, 'dist/');
 var pathToBuild = path.join(pathToRoot, 'build/');
 
-var pathToTopojsonSrc = path.join(
-    path.dirname(require.resolve('sane-topojson')), 'dist/'
-);
+var pathToTopojsonSrc;
+try {
+    pathToTopojsonSrc = path.join(path.dirname(require.resolve('sane-topojson')), 'dist/');
+} catch(e) {
+    console.log([
+        '',
+        'WARN: Cannot resolve path to *sane-topojson* package.',
+        '  This can happen when one `npm link sane-topojson`',
+        '  and runs a command in a Docker container.',
+        '  There is nothing to worry, if you see this warning while running',
+        '  `npm run test-image`, `npm run test-export` or `npm run baseline` ;)',
+        ''
+    ].join('\n'));
+}
 
 var partialBundleNames = [
     'basic', 'cartesian', 'geo', 'gl3d', 'gl2d', 'mapbox', 'finance'