Add a missing requirement to requirements.txt

This is default in most installations -- but clearly not all.

diff --git a/requirements.txt b/requirements.txt
index 3dfa624b955c1988e50dee4932ad774b38704009..b2cb3ad5e5f319601d9b4910fd7147514b653c9e 100644 (file)
--- a/requirements.txt
+++ b/requirements.txt
@@ -9,3 +9,4 @@ pycodestyle==2.4.0
 pynliner==0.8.0
 Babel==2.6.0
 bleach==3.1.4
+PyYAML==3.13