A klammer set's Python speaks through the log

Assembled from development commit d5f9c20b94b3. Since 5c29da5: a print() in
@eval, or in any Python a klammer set runs, is a log line -- on the
error stream under the command's name at -v 1, silent otherwise, never
in the document -- and K_log(level, text) is the builtin behind it; a
Python script using the binding keeps its own stdout. Previously such
output was lost, or on a terminal landed in the document.

tst/kpy_test.sh

@@ -276,6 +276,17 @@ except kt.Error as e:
 EOF
 expect "12a. an error inside a klammer body is located at the application" 'error 3 1 True'
 
+# The binding does NOT redirect sys.stdout: a print() in a document's @eval
+# is the host script's own stdout (under ktext it is a log line instead).
+run <<'EOF'
+import klammertext as kt
+M = kt.Machine(klammersets="none")
+M.read("@eval print('host stdout'); 1 @")
+print("result", M.apply())
+EOF
+expect "12b. a print() in @eval reaches the host script's stdout" 'host stdout
+result 1'
+
 run <<'EOF'
 import klammertext as kt
 try: