Tag calculation fix for aptly.publisher formula.

Prod-Related: PROD-36571
Change-Id: I68c801980851fd60550a417671d737d2f9987c6b
diff --git a/tests/test-requirements.txt b/tests/test-requirements.txt
index 0480052..979176f 100644
--- a/tests/test-requirements.txt
+++ b/tests/test-requirements.txt
@@ -1,3 +1,4 @@
 jsonschema
 reno
-setuptools<45.0.0
\ No newline at end of file
+setuptools<45.0.0
+msgpack<1.0.0
\ No newline at end of file