Report wrapped pub exceptions with --verbose and --trace.

sdk/lib/_internal/pub/lib/src/solver/version_solver.dart

Index: sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
diff --git a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
index aff70422f8c4ba3c9ce351b01bc4f270c3b16113..7e1c52e3a878f4fef9cda0f47f19a12b7e5d1201 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
+++ b/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
@@ -172,6 +172,9 @@ abstract class SolveFailure implements ApplicationException {
   /// an empty collection if the failure is not specific to one package.
   final Iterable<Dependency> dependencies;
 
+  final innerError = null;
+  final innerTrace = null;
+
   SolveFailure(this.package, Iterable<Dependency> dependencies)
       : dependencies = dependencies != null ? dependencies : <Dependency>[];