Try setting PERCY_PARALLEL_TOTAL to 1 temporarily

Author: carols10cents

package.json

@@ -25,7 +25,7 @@
     "start:live": "./script/ember.sh serve --proxy https://crates.io",
     "start:local": "./script/ember.sh serve --proxy http://127.0.0.1:8888",
     "start:staging": "./script/ember.sh serve --proxy https://staging-crates-io.herokuapp.com",
-    "test": "percy exec -- ember exam --split=2 --parallel",
+    "test": "PERCY_PARALLEL_TOTAL=1 percy exec -- ember exam --split=2 --parallel",
     "test-coverage": "COVERAGE=true npm run test && ember coverage-merge && rm -rf coverage_* coverage/coverage-summary.json && nyc report"
   },
   "devDependencies": {