[pushed] [gdb/testsuite] Require allow_python_tests in gdb.cp/pretty-print.exp

I build gdb without python support, and ran into:
...
(gdb) source $src/gdb/testsuite/gdb.cp/pretty-print.py
$src/gdb/testsuite/gdb.cp/pretty-print.py:18: Error in sourced command file:
Undefined command: "import".  Try "help".
(gdb) ERROR: Undefined command "source $src/gdb/testsuite/gdb.cp/pretty-print.py".
...

Fix this by requiring allow_python_tests.
---
 gdb/testsuite/gdb.cp/pretty-print.exp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gdb/testsuite/gdb.cp/pretty-print.exp b/gdb/testsuite/gdb.cp/pretty-print.exp
index eaeffc6c5f6..76c3b715668 100644
--- a/gdb/testsuite/gdb.cp/pretty-print.exp
+++ b/gdb/testsuite/gdb.cp/pretty-print.exp
@@ -16,6 +16,8 @@
 # Print std::string::npos using c++ pretty-printer.  Todo: convert this to a
 # DWARF assembly test-case, such that the regression test also works for clang.
 
+require allow_python_tests
+
 standard_testfile .cc
 
 set opts {}

base-commit: a58e6081294fd3dde8fc7397f3a09f8c8a3f87aa
-- 
2.51.0