Remove deprecated_internalProblem.

pkg/front_end/lib/src/fasta/command_line.dart

Index: pkg/front_end/lib/src/fasta/command_line.dart
diff --git a/pkg/front_end/lib/src/fasta/command_line.dart b/pkg/front_end/lib/src/fasta/command_line.dart
index 9f95255ec4ca82ef6c762a4190f06e4ca88af707..a36c59d6da6096aabbf3a5bf1bacca28f2cdba6d 100644
--- a/pkg/front_end/lib/src/fasta/command_line.dart
+++ b/pkg/front_end/lib/src/fasta/command_line.dart
@@ -6,8 +6,9 @@ library fasta.command_line;
 
 import 'fasta_codes.dart' show Message, templateFastaCLIArgumentRequired;
 
-import 'deprecated_problems.dart'
-    show deprecated_inputError, deprecated_internalProblem;
+import 'deprecated_problems.dart' show deprecated_inputError;
+
+import 'problems.dart' show unhandled;
 
 deprecated_argumentError(Message usage, String message) {
   if (usage != null) print(usage.message);
@@ -166,7 +167,8 @@ class CommandLine {
                     "'$valueSpecification', try using a type literal instead.");
               } else {
                 // All possible cases should have been handled above.
-                return deprecated_internalProblem("assertion failure");
+                return unhandled("${valueSpecification.runtimeType}",
+                    "CommandLine.parse", -1, null);
               }
               result.options[argument] = parsedValue;
               break;