py-dbus: Update python dbus bindings to 1.2.6.

D-Bus Python Bindings 1.2.6 (2018-01-29)
========================================

The “doppler radar” release.

Dependencies:

• When using Python 2, version 2.7 is now required. Python 2.6 security
  support ended in 2013.
• When using Python 3, version 3.4 or later is now required.
  Python 3.2 security support ended in 2016, and Python 3.3 security
  support ended in 2017.
• Most unit tests now require the tap.py module from PyPI.
• The deprecated dbus-glib library is no longer required. A bundled copy
  of its main loop integration code is included instead.
• GLib version 2.40 or later is required.
• libdbus version 1.8 or later is required.

Enhancements:

• AX_PYTHON_DEVEL is now used to find the CPPFLAGS, LDFLAGS and libraries
  needed to link test-import-repeatedly to libpython, which should reduce
  the number of wheels reinvented here.

• Remove workarounds for Python 2.6 limitations

• All unit tests now produce structured output (TAP)

Fixes:

• Fix a NULL dereference in constructing a Server if the underlying C
  function fails

• Silence compiler warnings triggered by the Python headers under gcc 7

• Avoid __gtype__ appearing in documentation, for reproducible builds

• Rename _dbus_bindings/ and _dbus_glib_bindings/ source directories to
  dbus_bindings/ and dbus_glib_bindings/ to avoid an ImportWarning
  appearing in the API documentation, which made the documentation build
  non-reproducible

(wiz)