Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/lib/src/exceptions.dart

Index: sdk/lib/_internal/pub_generated/lib/src/exceptions.dart
diff --git a/sdk/lib/_internal/pub/lib/src/exceptions.dart b/sdk/lib/_internal/pub_generated/lib/src/exceptions.dart
similarity index 77%
copy from sdk/lib/_internal/pub/lib/src/exceptions.dart
copy to sdk/lib/_internal/pub_generated/lib/src/exceptions.dart
index 65dff3fd0008a81374e5ad834e7311af19c03a4c..7d4f5a39b924a01604f200ad93a0e146350f8edb 100644
--- a/sdk/lib/_internal/pub/lib/src/exceptions.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/exceptions.dart
@@ -81,22 +81,28 @@ class PackageNotFoundException extends WrappedException {
 }
 
 /// All the names of user-facing exceptions.
-final _userFacingExceptions = new Set<String>.from([
-  'ApplicationException', 'GitException',
-  // This refers to http.ClientException.
+final _userFacingExceptions = new Set<String>.from(
+    ['ApplicationException', 'GitException', // This refers to http.ClientException.
   'ClientException',
-  // Errors coming from the Dart analyzer are probably caused by syntax errors
+      // Errors coming from the Dart analyzer are probably caused by syntax errors
   // in user code, so they're user-facing.
-  'AnalyzerError', 'AnalyzerErrorGroup',
-  // An error spawning an isolate probably indicates a transformer with an
+  'AnalyzerError',
+      'AnalyzerErrorGroup',
+      // An error spawning an isolate probably indicates a transformer with an
   // invalid import.
-  'IsolateSpawnException',
-  // IOException and subclasses.
-  'CertificateException', 'FileSystemException', 'HandshakeException',
-  'HttpException', 'IOException', 'ProcessException', 'RedirectException',
-  'SignalException', 'SocketException', 'StdoutException', 'TlsException',
-  'WebSocketException'
-]);
+  'IsolateSpawnException', // IOException and subclasses.
+  'CertificateException',
+      'FileSystemException',
+      'HandshakeException',
+      'HttpException',
+      'IOException',
+      'ProcessException',
+      'RedirectException',
+      'SignalException',
+      'SocketException',
+      'StdoutException',
+      'TlsException',
+      'WebSocketException']);
 
 /// Returns whether [error] is a user-facing error object.
 ///
@@ -109,11 +115,11 @@ bool isUserFacingException(error) {
   // TODO(nweiz): unify this list with _userFacingExceptions when issue 5897 is
   // fixed.
   return error is ApplicationException ||
-    error is AnalyzerError ||
-    error is AnalyzerErrorGroup ||
-    error is IsolateSpawnException ||
-    error is IOException ||
-    error is http.ClientException ||
-    error is YamlException ||
-    error is UsageException;
+      error is AnalyzerError ||
+      error is AnalyzerErrorGroup ||
+      error is IsolateSpawnException ||
+      error is IOException ||
+      error is http.ClientException ||
+      error is YamlException ||
+      error is UsageException;
 }