Index: tests/pybin/tools.py
===================================================================
--- tests/pybin/tools.py	(revision 9509a4120499e875cf40687b1ab935b179fa5d44)
+++ tests/pybin/tools.py	(revision 7a8f62c3b4eb778892c95845d9cfbbf5e3c0d521)
@@ -238,5 +238,5 @@
 # helper function to check if a files contains only a specific string
 def file_contains_only(file, text) :
-	with open(file) as f:
+	with open(file, encoding="latin-1") as f: # use latin-1 so all chars mean something.
 		ff = f.read().strip()
 		result = ff == text.strip()