Merge pull request #5489 from graingert/fix-safe-str-doc

fix safe_str docstring

src/_pytest/compat.py

@@ -377,7 +377,7 @@ def safe_str(v):
 else:
 
     def safe_str(v):
-        """returns v as string, converting to ascii if necessary"""
+        """returns v as string, converting to utf-8 if necessary"""
         try:
             return str(v)
         except UnicodeError: