Restore partial analysis of analysis options files

pkg/analyzer_cli/lib/src/analyzer_impl.dart

Index: pkg/analyzer_cli/lib/src/analyzer_impl.dart
diff --git a/pkg/analyzer_cli/lib/src/analyzer_impl.dart b/pkg/analyzer_cli/lib/src/analyzer_impl.dart
index 4b9a88e4197f9b2c07f0d2c3bd7e2e67fe770bd3..b3b94a92cab545db6bcfe8210938a7f098d66c6d 100644
--- a/pkg/analyzer_cli/lib/src/analyzer_impl.dart
+++ b/pkg/analyzer_cli/lib/src/analyzer_impl.dart
@@ -169,7 +169,7 @@ class AnalyzerImpl {
         : context.computeKindOf(librarySource);
     if (librarySourceKind == SourceKind.PART) {
       stderr.writeln("Only libraries can be analyzed.");
-      stderr.writeln("${path} is a part and can not be analyzed.");
+      stderr.writeln("$path is a part and can not be analyzed.");
       return ErrorSeverity.ERROR;
     }