Clean up dart:io exceptions.

sdk/lib/_internal/pub/lib/src/hosted_source.dart

Index: sdk/lib/_internal/pub/lib/src/hosted_source.dart
diff --git a/sdk/lib/_internal/pub/lib/src/hosted_source.dart b/sdk/lib/_internal/pub/lib/src/hosted_source.dart
index beabfd1d3d6f773ab54aedaa43b78287013aa326..6967aa6bf24e99d40d7ba09938d44c792c952540 100644
--- a/sdk/lib/_internal/pub/lib/src/hosted_source.dart
+++ b/sdk/lib/_internal/pub/lib/src/hosted_source.dart
@@ -156,7 +156,7 @@ class HostedSource extends Source {
       fail('Timed out trying to find package "$package" at $url.');
     }
 
-    if (error is io.SocketIOException) {
+    if (error is io.SocketException) {
       fail('Got socket error trying to find package "$package" at $url.\n'
           '${error.osError}');
     }