In Python 3 `super()` can be used without an argument
in order to get the parent class, `super()`.
In Python 2 the present class must be used as an argument,
`super(ThisClass, self)`.
This commit is done to support Python 2,
as without it all Gui Command tools will be broken
and will fail to launch, even if the unit tests pass.
Also, set the `__metaclass__` variable to `type`.
This is done to turn all classes into "new style" classes
in Python 2. This is required so `super()` works correctly
in this version of Pyton.
This commit can be reverted once Python 2 support
is completely dropped, and only Python 3 compatible code
is used.
Occasionally it fails to join lines even if the lines
visually share a point.
This is a rounding error in the comparison of the shared point;
a small distance will result in the points being considered
different and thus the lines not joining.
The solution is to test properly the two points using
`DraftVecUtils.equals` which considers the value of
the `precision` set in the Draft preferences.
