Fix Subprocess kwargs (#98)

start_new_session is an argument in fresh python, old use:
  `preexec_fn = os.setsid`

Author: penguinolog

exec_helpers/__init__.py

@@ -51,7 +51,7 @@
     "ExecResult",
 )
 
-__version__ = "1.9.0"
+__version__ = "1.9.1"
 __author__ = "Alexey Stepanov"
 __author_email__ = "penguinolog@gmail.com"
 __maintainers__ = {

exec_helpers/_subprocess_helpers.py

@@ -19,6 +19,7 @@
 
 __all__ = ("kill_proc_tree", "subprocess_kw")
 
+import os
 import platform
 
 # pylint: disable=unused-import
@@ -58,4 +59,4 @@ def kill_proc_tree(pid, including_parent=True):  # type:(int, bool) -> None  # p
 if "Windows" == platform.system():  # pragma: no cover
     subprocess_kw["creationflags"] = 0x00000200
 else:  # pragma: no cover
-    subprocess_kw["start_new_session"] = True
+    subprocess_kw["preexec_fn"] = os.setsid