bpo-43859: Improve the error message for IndentationError exceptions (GH-25431)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index d93b0f16..e0e8191 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -179,7 +179,7 @@ def ckmsg(src, msg, exception=SyntaxError):
 
         # should not apply to subclasses, see issue #31161
         s = '''if True:\nprint "No indent"'''
-        ckmsg(s, "expected an indented block", IndentationError)
+        ckmsg(s, "expected an indented block after 'if' statement on line 1", IndentationError)
 
         s = '''if True:\n        print()\n\texec "mixed tabs and spaces"'''
         ckmsg(s, "inconsistent use of tabs and spaces in indentation", TabError)