Switch to rustup hyper backend temporarily
diff --git a/appveyor.yml b/appveyor.yml
index b6c666c..b58168c 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,4 +1,9 @@
 environment:
+  # When this was added there were revocation check failures when using the
+  # libcurl backend as libcurl checks by default, but rustup doesn't provide the
+  # switch to turn this off. Switch to Hyper which looks to not check for
+  # revocation by default like libcurl does.
+  RUSTUP_USE_HYPER: 1
   matrix:
   - TARGET: x86_64-pc-windows-gnu
     MSYS2_BITS: 64