make sure the builtin help function doesn't fail when sys.stdin is not a valid file (closes #11709)

Original patch by Amaury Forgeot d'Arc with a test by bdettmer.

1 files changed, 2 insertions, 0 deletions

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 2dee6eee23..cc43684f19 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1417,6 +1417,8 @@ def pager(text):
 
 def getpager():
     """Decide what method to use for paging through text."""
+    if not hasattr(sys.stdin, "isatty"):
+        return plainpager
     if not hasattr(sys.stdout, "isatty"):
         return plainpager
     if not sys.stdin.isatty() or not sys.stdout.isatty():