The possible values for the contexts are `Load` ('a'), `Del` ('del a'),
`Store` ('a = 4') and the nodes that got the new attribute are Starred,
Subscript, List and Tuple. The builtin ast module provides contexts for
Name and Attribute as well, but we took a different approach in the past,
by having different nodes for each type of context. For instance, Name
used in a Del context is a DelName, while Name used in a Store
context is AssignName. Since this is ingrained in astroid since quite
some time, it makes no sense to change them as well, even though it's
a loss of consistency.
The patch introduces a new dependency to enum34 on older Python
versions, which is used for building the three possible enum values
for the contexts.

Closes issue #267.

The first name will exist until astroid 2.0.

They are subclasses of AstroidBuildingException and are raised when
a module can't be imported from various reasons.
Also do_import_module lets the errors to bubble up without converting
them to InferenceError. This particular conversion happens only
during the inference.

They used to have different signatures and each one made
assumptions about what could be passed to other implementations,
leading to various possible crashes when one or more arguments
weren't given. Closes issue #277.

 to avoid a potential problem with encodings when using .format.


Closes issue #273.

Some object, for instance List or Tuple can have, after inference,
Uninferable as their elements, happening when their components
weren't couldn't be inferred properly. This means that as_string
needs to cope with expecting Uninferable nodes part of the other
nodes coming for a string transformation. The patch adds a visit
method in AsString and ``accept`` on Yes / Uninferable nodes.
Closes issue #270.