Fonttools related tracebacks in Python 3 CI runs

[rahulporuri]

The tracebacks can be found on the job https://ci.appveyor.com/project/EnthoughtOSS/chaco-euxdv/builds/25137381/job/hmdrf33ru6tbxxa2

Note that both the 3.5 and 3.6 appveyor CI jobs finished running the tests successfully.

appveyor-run.cmd test %runtime% %toolkits%
Running tests in 'chaco-test-3.5-null'
copying file to tempdir: .coveragerc
[EXECUTING] edm run -e chaco-test-3.5-null -- coverage run -m unittest discover -v chaco
Could not covert font to FontEntry for file c:\windows\fonts\ebrima.ttf
Traceback (most recent call last):
  File "c:\users\appveyor\.edm\envs\chaco-test-3.5-null\lib\site-packages\kiva\fonttools\font_manager.py", line 1440, in <module>
    fontManager = pickle_load(_fmcache)
  File "c:\users\appveyor\.edm\envs\chaco-test-3.5-null\lib\site-packages\kiva\fonttools\font_manager.py", line 1050, in pickle_load
    fh = open(filename, 'rb')
FileNotFoundError: [Errno 2] No such file or directory: 'C:\\Users\\appveyor\\AppData\\Roaming\\Enthought\\kiva\\fontList.cache'

Originally posted by @rahulporuri in #445 (comment)

[jvkersch]

This should probably be backed by an Enable issue.

[kitchoi]

Opened: enthought/enable#363

This is probably related: enthought/enable#362

[rahulporuri]

closing as the underlying enable issues have been closed which probably fixes this issue as well