Error of `Segmentation fault` is raised when a patched function is called where there is no `print` function inside the payload

[NaleRaphael]

Steps to reproduce this issue:

1. comment out the print function in demo/run_patched_module.py at line 61.
   

   bytejection/demo/run_patch_module.py

   Lines 59 to 62 in 67a9ca2

   	# Payload to be injected
   	def new_verification():
   	print('... Content has been modified ...')

2. add arbitrary code to make that function work normally. (just make sure there is no print function in it)
3. repeat the function call modified.foo() as line 73 more than 3 times.
   

   bytejection/demo/run_patch_module.py

   Lines 70 to 73 in 67a9ca2

   	# Check the output of modified function
   	print('--- modified version ---')
   	modified_mod = load_module_from_path('modified', osp.join(THIS_DIR, 'modified.pyc'))
   	modified_mod.foo()

4. execute demo/run_patched_module.py.

Result of execution:

• Ubuntu 18.04, Python 3.6.9 (with gdb):

--- modified version ---
foo
foo
foo
Fatal Python error: deletion of interned string failed
KeyError: ''eyError'

Current thread 0x00007ffff7fd7740 (most recent call first):
  File "/media/nale/Data/Users/nale/project/bytejection/demo/pkg/foobarbuzz/core.py", line 8 in foo
  File "run_patch_module.py", line 78 in main
  File "run_patch_module.py", line 90 in <module>

Program received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.

• Ubuntu 18.04, Python 3.7.4 (with gdb):

--- modified version ---
foo

Program received signal SIGSEGV, Segmentation fault.
PyFunction_NewWithQualName ()
    at /tmp/build/80754af9/python_1565725737370/work/Objects/funcobject.c:33
33	/tmp/build/80754af9/python_1565725737370/work/Objects/funcobject.c: No such file or directory.