Remove no_proxy variables

no_proxy was newer supported by debmirror
also allow empty *_proxy env values in order to bypass
system-defined proxy settings

Closes-bug: PROD-35868
Change-Id: Id55cd877f6af3a9dd52e0c16a720fa9efe620c0c
diff --git a/tests/test-requirements.txt b/tests/test-requirements.txt
index 7188b2b..bc7dc7f 100644
--- a/tests/test-requirements.txt
+++ b/tests/test-requirements.txt
@@ -1,3 +1,4 @@
 jsonschema
 reno
 setuptools<45.0.0
+msgpack<1.0.0