No tkinter package available
In Python 2.7, the Tkinter package name is Tkinter instead of the Python 3 tkinter. When I look at your error, it seems that your matplotlib is a Python 3 script.
If you have written matplotlib (at /usr/local/lib64/python2.7/site-packages/matplotlib/backends/backend_tkagg.py) yourself (and it is written for Python 2.7), change line 6 from
from six.moves import tkinter as Tkto
from six.moves import Tkinter as Tkor a more version-friendly:
try: from six.moves import tkinter as Tk # print('Python 3')except ImportError e: from six.moves import Tkinter as Tk # print 'Python 2.7'If you haven't written matplotlib yourself, find a different install(er) for Python 2.7. If this doesn't work, use the fix above and report the issue by contacting the administrator of matplotlib.