CorefileFinder.read returns bytes instead of str type

[marinelay]

Create test.py like:

from pwnlib.tubes.process import process
from pwnlib.elf.corefile import CorefileFinder

p = process('cat')
p.shutdown('send')
p.wait_for_close()

c = CorefileFinder(p)
c.apport_corefile()

then it raises TypeError: initial_value must be str or None, not bytes like this:

Traceback (most recent call last):
  File "/home/wonseok/current/pwntools/my_test.py", line 7, in <module>
    c = CorefileFinder(p)
  File "/home/wonseok/current/pwntools/pwnlib/elf/corefile.py", line 1197, in __init__
    self.core_path = self.native_corefile()
  File "/home/wonseok/current/pwntools/pwnlib/elf/corefile.py", line 1372, in native_corefile
    return self.native_corefile_pipe()
  File "/home/wonseok/current/pwntools/pwnlib/elf/corefile.py", line 1390, in native_corefile_pipe
    apport_core = self.apport_corefile()
  File "/home/wonseok/current/pwntools/pwnlib/elf/corefile.py", line 1262, in apport_corefile
    return self.apport_crash_extract_corefile(crash_data)
  File "/home/wonseok/current/pwntools/pwnlib/elf/corefile.py", line 1273, in apport_crash_extract_corefile
    file = StringIO(crashfile_data)
TypeError: initial_value must be str or None, not bytes

pwntools/pwnlib/elf/corefile.py

Lines 1309 to 1332 in 5981c72

	def apport_read_crash_data(self):
	"""Find the apport crash for the process
	Returns:
	`str`: Raw contents of the crash file or ``None``.
	"""
	uid = self.uid
	crash_name = self.exe.replace('/', '_')
	crash_path = '/var/crash/%s.%i.crash' % (crash_name, uid)
	try:
	log.debug("Looking for Apport crash at %r" % crash_path)
	data = self.read(crash_path)
	except Exception:
	return None
	# Remove the crash file, so that future crashes will be captured
	try:
	self.unlink(crash_path)
	except Exception:
	pass
	return data

The cause is that apport_read_crash_data method returns bytes because self.read at line 1322 can return bytes instead of str.
I think that type casting can be solution before return statement.
If I missed something, please let me know.

Thank you.

[sanjitkumar2016]

#2387