[yt-dev] Issue #666: Grids callback is broken in 3.0 (yt_analysis/yt)

[Nathan Goldbaum]

New issue 666: Grids callback is broken in 3.0
https://bitbucket.org/yt_analysis/yt/issue/666/grids-callback-is-broken-in-30

Nathan Goldbaum:


```
#!python

  File "/usr/local/bin/yt", line 9, in <module>
    load_entry_point('yt==3.0dev', 'console_scripts', 'yt')()
  File "/Users/goldbaum/Documents/yt-3.0/yt/utilities/command_line.py", line 1701, in run_main
    args.func(args)
  File "/Users/goldbaum/Documents/yt-3.0/yt/utilities/command_line.py", line 87, in run
    self(args)
  File "/Users/goldbaum/Documents/yt-3.0/yt/utilities/command_line.py", line 1317, in __call__
    plt.annotate_grids()
  File "/Users/goldbaum/Documents/yt-3.0/yt/visualization/plot_window.py", line 98, in newfunc
    args[0]._setup_plots()
  File "/Users/goldbaum/Documents/yt-3.0/yt/visualization/plot_window.py", line 963, in _setup_plots
    self.run_callbacks(f)
  File "/Users/goldbaum/Documents/yt-3.0/yt/visualization/plot_window.py", line 983, in run_callbacks
    callback(cbw)
  File "/Users/goldbaum/Documents/yt-3.0/yt/visualization/plot_modifications.py", line 365, in __call__
    GLE = plot.data.grid_left_edge
AttributeError: 'YTSlice' object has no attribute 'grid_left_edge'
```

The solution is to grab the grid left edges from the geometry handler.