pyzfs: python3 support (library 1/2)

These changes are efficient and valid in python 2 and 3. For the
most part, they are also pythonic.

* 2to3 conversion
* add __future__ imports
* iterator changes
* integer division
* relative import fixes

Reviewed-by: John Ramsden <johnramsden@riseup.net>
Reviewed-by: Neal Gompa <ngompa@datto.com>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
Closes #8096

contrib/pyzfs/libzfs_core/__init__.py

@@ -38,6 +38,7 @@
 
     Maximum length of any ZFS name.
 '''
+from __future__ import absolute_import, division, print_function
 
 from ._constants import (
     MAXNAMELEN,

contrib/pyzfs/libzfs_core/_constants.py

@@ -18,10 +18,12 @@
 Important `libzfs_core` constants.
 """
 
+from __future__ import absolute_import, division, print_function
+
 
 # https://stackoverflow.com/a/1695250
 def enum(*sequential, **named):
-    enums = dict(zip(sequential, range(len(sequential))), **named)
+    enums = dict(((b, a) for a, b in enumerate(sequential)), **named)
     return type('Enum', (), enums)
 
 

contrib/pyzfs/libzfs_core/_error_translation.py

@@ -26,6 +26,7 @@
 
 The parameters and exceptions are documented in the `libzfs_core` interfaces.
 """
+from __future__ import absolute_import, division, print_function
 
 import errno
 import re
@@ -102,8 +103,9 @@ def lzc_snapshot_translate_errors(ret, errlist, snaps, props):
 
     def _map(ret, name):
         if ret == errno.EXDEV:
-            pool_names = map(_pool_name, snaps)
-            same_pool = all(x == pool_names[0] for x in pool_names)
+            pool_names = iter(map(_pool_name, snaps))
+            pool_name = next(pool_names, None)
+            same_pool = all(x == pool_name for x in pool_names)
             if same_pool:
                 return lzc_exc.DuplicateSnapshots(name)
             else:
@@ -270,7 +272,8 @@ def _map(ret, name):
 def lzc_release_translate_errors(ret, errlist, holds):
     if ret == 0:
         return
-    for _, hold_list in holds.iteritems():
+    for snap in holds:
+        hold_list = holds[snap]
         if not isinstance(hold_list, list):
             raise lzc_exc.TypeError('holds must be in a list')
 
@@ -705,15 +708,17 @@ def _handle_err_list(ret, errlist, names, exception, mapper):
 
     if len(errlist) == 0:
         suppressed_count = 0
+        names = list(zip(names, range(2)))
         if len(names) == 1:
-            name = names[0]
+            name, _ = names[0]
         else:
             name = None
         errors = [mapper(ret, name)]
     else:
         errors = []
         suppressed_count = errlist.pop('N_MORE_ERRORS', 0)
-        for name, err in errlist.iteritems():
+        for name in errlist:
+            err = errlist[name]
             errors.append(mapper(err, name))
 
     raise exception(errors, suppressed_count)

contrib/pyzfs/libzfs_core/_libzfs_core.py

@@ -26,6 +26,7 @@
 are directly returned.  Error conditions are signalled by exceptions
 rather than by integer error codes.
 """
+from __future__ import absolute_import, division, print_function
 
 import errno
 import functools
@@ -485,8 +486,8 @@ def lzc_hold(holds, fd=None):
     errors.lzc_hold_translate_errors(ret, errlist, holds, fd)
     # If there is no error (no exception raised by _handleErrList), but errlist
     # is not empty, then it contains missing snapshots.
-    assert all(x == errno.ENOENT for x in errlist.itervalues())
-    return errlist.keys()
+    assert all(errlist[x] == errno.ENOENT for x in errlist)
+    return list(errlist.keys())
 
 
 def lzc_release(holds):
@@ -521,7 +522,8 @@ def lzc_release(holds):
     '''
     errlist = {}
     holds_dict = {}
-    for snap, hold_list in holds.iteritems():
+    for snap in holds:
+        hold_list = holds[snap]
         if not isinstance(hold_list, list):
             raise TypeError('holds must be in a list')
         holds_dict[snap] = {hold: None for hold in hold_list}
@@ -531,8 +533,8 @@ def lzc_release(holds):
     errors.lzc_release_translate_errors(ret, errlist, holds)
     # If there is no error (no exception raised by _handleErrList), but errlist
     # is not empty, then it contains missing snapshots and tags.
-    assert all(x == errno.ENOENT for x in errlist.itervalues())
-    return errlist.keys()
+    assert all(errlist[x] == errno.ENOENT for x in errlist)
+    return list(errlist.keys())
 
 
 def lzc_get_holds(snapname):
@@ -1873,9 +1875,9 @@ def lzc_get_props(name):
         mountpoint_val = '/' + name
     else:
         mountpoint_val = None
-    result = {k: v['value'] for k, v in result.iteritems()}
+    result = {k: result[k]['value'] for k in result}
     if 'clones' in result:
-        result['clones'] = result['clones'].keys()
+        result['clones'] = list(result['clones'].keys())
     if mountpoint_val is not None:
         result['mountpoint'] = mountpoint_val
     return result

contrib/pyzfs/libzfs_core/_nvlist.py

@@ -47,6 +47,7 @@
 - a value can be a list of dictionaries that adhere to this format
 - all elements of a list value must be of the same type
 """
+from __future__ import absolute_import, division, print_function
 
 import numbers
 from collections import namedtuple

contrib/pyzfs/libzfs_core/bindings/__init__.py

@@ -19,6 +19,7 @@
 `libzfs_core` uses.  The modules expose CFFI objects required
 to make calls to functions in the libraries.
 """
+from __future__ import absolute_import, division, print_function
 
 import threading
 import importlib
@@ -47,7 +48,7 @@ def __getattr__(self, name):
     ffi = FFI()
 
     for module_name in MODULES:
-        module = importlib.import_module("." + module_name, __package__)
+        module = importlib.import_module("." + module_name, __name__)
         ffi.cdef(module.CDEF)
         lib = LazyLibrary(ffi, module.LIBRARY)
         setattr(module, "ffi", ffi)

contrib/pyzfs/libzfs_core/bindings/libnvpair.py

@@ -17,6 +17,7 @@
 """
 Python bindings for ``libnvpair``.
 """
+from __future__ import absolute_import, division, print_function
 
 CDEF = """
     typedef ... nvlist_t;

contrib/pyzfs/libzfs_core/bindings/libzfs_core.py

@@ -17,6 +17,7 @@
 """
 Python bindings for ``libzfs_core``.
 """
+from __future__ import absolute_import, division, print_function
 
 CDEF = """
 

contrib/pyzfs/libzfs_core/ctypes.py

@@ -17,6 +17,7 @@
 """
 Utility functions for casting to a specific C type.
 """
+from __future__ import absolute_import, division, print_function
 
 from .bindings.libnvpair import ffi as _ffi
 

contrib/pyzfs/libzfs_core/exceptions.py

@@ -17,6 +17,7 @@
 """
 Exceptions that can be raised by libzfs_core operations.
 """
+from __future__ import absolute_import, division, print_function
 
 import errno
 from ._constants import (