valgrind reports leaks in many python tests, such as:
==17162== VALGRIND_GDB_ERROR_BEGIN
==17162== 8,208 (5,472 direct, 2,736 indirect) bytes in 57 blocks are definitely lost in loss record 7,551 of 7,679
==17162==    at 0x4835753: malloc (vg_replace_malloc.c:307)
==17162==    by 0x6EAFD1: _PyObject_New (object.c:279)
==17162==    by 0x4720E6: blpy_iter(_object*) (py-block.c:92)
==17162==    by 0x698772: PyObject_GetIter (abstract.c:2577)
==17162==    by 0x2343BE: _PyEval_EvalFrameDefault (ceval.c:3159)
==17162==    by 0x22E9E2: function_code_fastcall (call.c:283)
==17162==    by 0x2340A8: _PyObject_Vectorcall (abstract.h:127)
==17162==    by 0x2340A8: call_function (ceval.c:4987)
==17162==    by 0x2340A8: _PyEval_EvalFrameDefault (ceval.c:3486)
==17162==    by 0x22E9E2: function_code_fastcall (call.c:283)
==17162==    by 0x82172B: _PyObject_Vectorcall (abstract.h:127)
==17162==    by 0x82172B: method_vectorcall (classobject.c:67)
==17162==    by 0x6AF474: _PyObject_Vectorcall (abstract.h:127)
==17162==    by 0x6AF474: _PyObject_CallNoArg (abstract.h:153)
==17162==    by 0x6AF474: _PyObject_CallFunctionVa (call.c:914)
==17162==    by 0x6B0673: callmethod (call.c:1010)
==17162==    by 0x6B0673: _PyObject_CallMethod_SizeT (call.c:1103)
==17162==    by 0x477DFE: gdb_PyObject_CallMethod<> (python-internal.h:182)
==17162==    by 0x477DFE: get_py_iter_from_func(_object*, char const*) (py-framefilter.c:272)
==17162==    by 0x4791B4: py_print_args (py-framefilter.c:706)
==17162==    by 0x4791B4: py_print_frame(_object*, enum_flags<frame_filter_flag>, ext_lang_frame_args, ui_out*, int, htab*) (py-framefilter.c:960)
==17162==    by 0x47A130: gdbpy_apply_frame_filter(extension_language_defn const*, frame_info*, enum_flags<frame_filter_flag>, ext_lang_frame_args, ui_out*, int, int) (py-framefilter.c:1236)
==17162==    by 0x369C39: apply_ext_lang_frame_filter(frame_info*, enum_flags<frame_filter_flag>, ext_lang_frame_args, ui_out*, int, int) (extension.c:563)
==17162==    by 0x4EC9C9: backtrace_command_1 (stack.c:2031)
==17162==    by 0x4EC9C9: backtrace_command(char const*, int) (stack.c:2183)
...

Most of the leaks in python tests are due to the fact that many
PyObject xxxxx_dealloc functions are missing the line to free self
or obj such as:
   Py_TYPE (self)->tp_free (self);
or
   Py_TYPE (obj)->tp_free (obj);

With this patch, the number of python tests leaking decreases from 52 to 12.

gdb/ChangeLog

2019-11-18  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* python/py-block.c (blpy_dealloc): Call tp_free.
	(blpy_block_syms_dealloc): Likewise.
	* python/py-finishbreakpoint.c (bpfinishpy_dealloc): Likewise.
	* python/py-inferior.c (infpy_dealloc): Likewise.
	* python/py-lazy-string.c (stpy_dealloc): Likewise.
	* python/py-linetable.c (ltpy_iterator_dealloc): Likewise.
	* python/py-symbol.c (sympy_dealloc): Likewise.
	* python/py-symtab.c (stpy_dealloc): Likewise.
	* python/py-type.c (typy_iterator_dealloc): Likewise.