Add PROMPT_TOOLKIT_NO_CPR=1 environment variable to disable CPR requests

See #886 (comment).

Author: asmeurer

prompt_toolkit/input/vt100.py

@@ -69,6 +69,8 @@ def __init__(self, stdin):
     def responds_to_cpr(self):
         # When the input is a tty, we assume that CPR is supported.
         # It's not when the input is piped from Pexpect.
+        if os.environ.get('PROMPT_TOOLKIT_NO_CPR', '') == '1':
+            return False
         return self.stdin.isatty()
 
     def attach(self, input_ready_callback):