Deprecate all diagnostics methods that use strings.

pkg/front_end/test/fasta/testing/suite.dart

Index: pkg/front_end/test/fasta/testing/suite.dart
diff --git a/pkg/front_end/test/fasta/testing/suite.dart b/pkg/front_end/test/fasta/testing/suite.dart
index ed6c64dc864660be9d018792e5d60b3cbbe53569..9d12364725f6bc05ee43fa9b008fea30f03b2cd3 100644
--- a/pkg/front_end/test/fasta/testing/suite.dart
+++ b/pkg/front_end/test/fasta/testing/suite.dart
@@ -32,7 +32,8 @@ import 'package:testing/testing.dart'
 
 import 'package:front_end/src/fasta/compiler_context.dart' show CompilerContext;
 
-import 'package:front_end/src/fasta/errors.dart' show InputError;
+import 'package:front_end/src/fasta/deprecated_problems.dart'
+    show deprecated_InputError;
 
 import 'package:front_end/src/fasta/testing/kernel_chain.dart'
     show MatchExpectation, Print, Verify, WriteDill;
@@ -269,7 +270,7 @@ class Outline extends Step<TestDescription, Program, FastaContext> {
           }
         }
       }
-    } on InputError catch (e, s) {
+    } on deprecated_InputError catch (e, s) {
       return fail(null, e.error, s);
     }
     context.programToTarget.clear();