Enable Boto workaround only on Python 3.x (issue paylogic#68)

Refer to issue 68 on GitHub for details:
  paylogic#68

pip_accel/__init__.py

@@ -1,7 +1,7 @@
 # Accelerator for pip, the Python package manager.
 #
 # Author: Peter Odding <[email protected]>
-# Last Change: February 19, 2016
+# Last Change: March 4, 2016
 # URL: https://github.com/paylogic/pip-accel
 #
 # TODO Permanently store logs in the pip-accel directory (think about log rotation).
@@ -77,7 +77,7 @@
 from pip.req import InstallRequirement
 
 # Semi-standard module versioning.
-__version__ = '0.42.4'
+__version__ = '0.42.5'
 
 # Initialize a logger for this module.
 logger = logging.getLogger(__name__)
@@ -781,27 +781,34 @@ class PatchedAttribute(object):
  exited.
  """
 
- def __init__(self, object, attribute, value):
+ def __init__(self, object, attribute, value, enabled=True):
  """
  Initialize a :class:`PatchedAttribute` object.
 
  :param object: The object whose attribute should be patched.
  :param attribute: The name of the attribute to be patched (a string).
  :param value: The temporary value for the attribute.
+ :param enabled: :data:`True` to patch the attribute, :data:`False` to
+ do nothing instead. This enables conditional attribute
+ patching while unconditionally using the
+ :keyword:`with` statement.
  """
  self.object = object
  self.attribute = attribute
  self.patched_value = value
  self.original_value = None
+ self.enabled = enabled
 
  def __enter__(self):
  """Change the object attribute when entering the context."""
- self.original_value = getattr(self.object, self.attribute)
- setattr(self.object, self.attribute, self.patched_value)
+ if self.enabled:
+ self.original_value = getattr(self.object, self.attribute)
+ setattr(self.object, self.attribute, self.patched_value)
 
  def __exit__(self, exc_type=None, exc_value=None, traceback=None):
  """Restore the object attribute when leaving the context."""
- setattr(self.object, self.attribute, self.original_value)
+ if self.enabled:
+ setattr(self.object, self.attribute, self.original_value)
 
 
 class AttributeOverrides(object):

pip_accel/caches/s3.py

@@ -3,7 +3,7 @@
 # Authors:
 # - Adam Feuer <[email protected]>
 # - Peter Odding <[email protected]>
-# Last Change: November 8, 2015
+# Last Change: March 4, 2016
 # URL: https://github.com/paylogic/pip-accel
 #
 # A word of warning: Do *not* use the cached_property decorator here, because
@@ -99,7 +99,7 @@
 # Modules included in our package.
 from pip_accel import PatchedAttribute
 from pip_accel.caches import AbstractCacheBackend
-from pip_accel.compat import urlparse
+from pip_accel.compat import PY3, urlparse
 from pip_accel.exceptions import CacheBackendDisabledError, CacheBackendError
 from pip_accel.utils import AtomicReplace, makedirs
 
@@ -361,6 +361,7 @@ def __init__(self):
  object=Config,
  attribute='get',
  value=self.get,
+ enabled=PY3,
  )
 
  def get(self, section, name, default=None, **kw):

pip_accel/compat.py

@@ -1,7 +1,7 @@
 # Accelerator for pip, the Python package manager.
 #
 # Author: Peter Odding <[email protected]>
-# Last Change: November 8, 2015
+# Last Change: March 4, 2016
 # URL: https://github.com/paylogic/pip-accel
 
 """Operating system detection and Python version compatibility."""
@@ -31,10 +31,12 @@
  from StringIO import StringIO
  from urllib import pathname2url
  from urlparse import urljoin, urlparse
+ PY3 = False
 except (ImportError, NameError):
  # Python 3.
  basestring = str
  import configparser
  from io import StringIO
  from urllib.parse import urljoin, urlparse
  from urllib.request import pathname2url
+ PY3 = True