feat(py-libzfs): drop lock from context manager

truenas/py-libzfs#250

nas_ports/devel/py-libzfs/files/patch-simple-context-manager

@@ -0,0 +1,40 @@
+diff --git libzfs.pyx libzfs.pyx
+index 6f9ac94..0b305df 100644
+--- libzfs.pyx
++++ libzfs.pyx
+@@ -21,7 +21,6 @@ from libc.stdlib cimport realloc
+ import errno as py_errno
+ import urllib.parse
+
+-GLOBAL_CONTEXT_LOCK = threading.Lock()
+ logger = logging.getLogger(__name__)
+
+
+@@ -519,24 +518,14 @@ cdef class ZFS(object):
+                 self.proptypes[t] = proptypes
+
+     def __enter__(self):
+-        GLOBAL_CONTEXT_LOCK.acquire()
+         return self
+
+     def __exit__(self, exc_type, value, traceback):
+-        self.__libzfs_fini()
+-        GLOBAL_CONTEXT_LOCK.release()
+-        if exc_type is not None:
+-            raise
+-
+-    def __libzfs_fini(self):
+-        if self.handle:
+-            with nogil:
+-                libzfs.libzfs_fini(self.handle)
+-
+-            self.handle = NULL
++        pass
+
+     def __dealloc__(self):
+-        ZFS.__libzfs_fini(self)
++        with nogil:
++            libzfs.libzfs_fini(self.handle)
+
+     def asdict(self):
+         return [p.asdict() for p in self.pools]