Clean up imports of old modules (#433)

Remove compatibility leftovers from earlier versions of Python.
Minimum version as of now is Python 3.6.

* import Queue dates to Python 2
* import collections.*Mapping was changed to collections.abc.*Mapping
  in Python 3.3
* import ConfigParser dates to Python 2
* import xml.etree.cElementTree is deprecated since Python 3.3. It
  will pick the fastest option when using xml.etree.ElementTree.

Fix some package relative imports to be consistent with surrounding code.

canopen/lss.py

@@ -1,10 +1,7 @@
 import logging
 import time
 import struct
-try:
-    import queue
-except ImportError:
-    import Queue as queue
+import queue
 
 logger = logging.getLogger(__name__)
 

canopen/network.py

@@ -1,7 +1,4 @@
-try:
-    from collections.abc import MutableMapping
-except ImportError:
-    from collections import MutableMapping
+from collections.abc import MutableMapping
 import logging
 import threading
 from typing import Callable, Dict, Iterable, List, Optional, Union

canopen/objectdictionary/__init__.py

@@ -3,10 +3,7 @@
 """
 import struct
 from typing import Dict, Iterable, List, Optional, TextIO, Union
-try:
-    from collections.abc import MutableMapping, Mapping
-except ImportError:
-    from collections import MutableMapping, Mapping
+from collections.abc import MutableMapping, Mapping
 import logging
 
 from canopen.objectdictionary.datatypes import *

canopen/objectdictionary/eds.py

@@ -1,11 +1,7 @@
 import copy
 import logging
 import re
-
-try:
-    from configparser import RawConfigParser, NoOptionError, NoSectionError
-except ImportError:
-    from ConfigParser import RawConfigParser, NoOptionError, NoSectionError
+from configparser import RawConfigParser, NoOptionError, NoSectionError
 
 from canopen import objectdictionary
 from canopen.objectdictionary import ObjectDictionary, datatypes

canopen/objectdictionary/epf.py

@@ -1,7 +1,4 @@
-try:
-    import xml.etree.cElementTree as etree
-except ImportError:
-    import xml.etree.ElementTree as etree
+import xml.etree.ElementTree as etree
 import logging
 
 from canopen import objectdictionary

canopen/pdo/__init__.py

@@ -4,7 +4,7 @@
 from canopen.pdo.base import PdoBase, Maps
 
 # Compatibility
-from .base import Variable
+from canopen.pdo.base import Variable
 
 logger = logging.getLogger(__name__)
 

canopen/pdo/base.py

@@ -1,10 +1,7 @@
 import threading
 import math
 from typing import Callable, Dict, Iterable, List, Optional, Union
-try:
-    from collections.abc import Mapping
-except ImportError:
-    from collections import Mapping
+from collections.abc import Mapping
 import logging
 import binascii
 

canopen/sdo/__init__.py

@@ -4,4 +4,4 @@
 from canopen.sdo.exceptions import SdoAbortedError, SdoCommunicationError
 
 # Compatibility
-from .base import Variable, Record, Array
+from canopen.sdo.base import Variable, Record, Array

canopen/sdo/base.py

@@ -1,9 +1,6 @@
 import binascii
 from typing import Iterable, Optional, Union
-try:
-    from collections.abc import Mapping
-except ImportError:
-    from collections import Mapping
+from collections.abc import Mapping
 
 from canopen import objectdictionary
 from canopen.objectdictionary import ObjectDictionary

canopen/sdo/client.py

@@ -2,10 +2,7 @@
 import logging
 import io
 import time
-try:
-    import queue
-except ImportError:
-    import Queue as queue
+import queue
 
 from canopen.network import CanError
 from canopen import objectdictionary

canopen/variable.py

@@ -1,9 +1,6 @@
 import logging
 from typing import Union
-try:
-    from collections.abc import Mapping
-except ImportError:
-    from collections import Mapping
+from collections.abc import Mapping
 
 from canopen import objectdictionary