Defer imports from font_manager in font module

[rahulporuri]

Deferring these imports means that a number of places where we need to import from font don't trigger the import time side-effect in the font_manager module.

This PR doesn't attempt to actually fix either of the issues #362 or #363 .

[codecov-io]

Codecov Report

Merging #368 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #368      +/-   ##
==========================================
+ Coverage   32.91%   32.91%   +<.01%     
==========================================
  Files         206      206              
  Lines       18303    18304       +1     
  Branches     2415     2415              
==========================================
+ Hits         6024     6025       +1     
  Misses      11893    11893              
  Partials      386      386

Impacted Files	Coverage Δ
kiva/fonttools/font.py	56.79% <100%> (+0.54%)	⬆️

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[jwiggins]

What is this fixing, if I may ask?

[rahulporuri]

this PR should fix this issue - enthought/chaco#448

[jwiggins]

Which references #362 and #363, neither of which are fixed here. Right?

[rahulporuri]

Which references #362 and #363, neither of which are fixed here. Right?

Yes. The actual issues i.e. import-time side effects of font_manager and inability to load font files are not addressed here.

This PR simply aims to defer the import-time side effects to when the objects are actually needed. Deferring the imports prevents the tracebacks/logs from appearing when kiva or kiva.fonttools.font.Font are used.

For example, at the moment, simply doing import kiva will cause the tracebacks to appear because kiva.__init__ imports from kiva.fonttools.font and kiva.fonttools.font imports from kiva.fonttools.font_manager.

There are also a few places where Font is instantiated by the relevant findfont or findfontname methods are not used. Those uses also now don't need to worry about seeing this import-time side effect.

Does that answer your question?

[jwiggins]

Yes, I think that's enough context.

[rahulporuri]

Thanks for the quick reviews John!