Fix a lockfile freshness checking bug.

lib/src/entrypoint.dart

Index: lib/src/entrypoint.dart
diff --git a/lib/src/entrypoint.dart b/lib/src/entrypoint.dart
index dc1a4a445f6f95eacab95ac2e73ee75c5f2fddd2..bbca8f10c4e459533a7a5b19f7588e69c34aa4c7 100644
--- a/lib/src/entrypoint.dart
+++ b/lib/src/entrypoint.dart
@@ -11,6 +11,7 @@ import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 
 import 'barback/asset_environment.dart';
+import 'exceptions.dart';
 import 'io.dart';
 import 'lock_file.dart';
 import 'log.dart' as log;
@@ -511,10 +512,15 @@ class Entrypoint {
     // since they're mutable and may have changed since the last get.
     return lockFile.packages.values.every((id) {
       var source = cache.sources[id.name];
-      if (source is! CachedSource) return true;
+      if (source is CachedSource) return true;
 
-      return cache.sources.load(id).dependencies.every((dep) =>
-          overrides.contains(dep.name) || _isDependencyUpToDate(dep));
+      try {
+        return cache.sources.load(id).dependencies.every((dep) =>
+            overrides.contains(dep.name) || _isDependencyUpToDate(dep));
+      } on FileException {
+        // If we can't load the pubpsec, the user needs to re-run "pub get".
+        return false;
+      }
     });
   }