Don't crash on str(figimage(...)).

anntzer · anntzer · commit 014c02b99d40 · 2019-04-12T20:35:45.000+02:00
`im = figimage(np.random.rand(100, 100), xo=100, yo=100); print(im)`

Previously:
```
Traceback (most recent call last):
  File "&lt;string&gt;", line 4, in &lt;module&gt;
  File "/usr/lib/python3.7/site-packages/matplotlib/image.py", line 184, in __str__
    return "AxesImage(%g,%g;%gx%g)" % tuple(self.axes.bbox.bounds)
AttributeError: 'NoneType' object has no attribute 'bbox'
```

now:
```
&lt;matplotlib.image.FigureImage object at 0x7fa97be63860&gt;
```

Note that `AxesImage` actually already has the same `__str__` defined in
its own body (which this PR leaves untouched).

Defining a proper `__str__` for `FigureImage` (and other `_ImageBase`
subclasses) is not the object of this PR.
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -177,9 +177,6 @@ def _rgb_to_rgba(A):
 class _ImageBase(martist.Artist, cm.ScalarMappable):
     zorder = 0
 
-    def __str__(self):
-        return "AxesImage(%g,%g;%gx%g)" % tuple(self.axes.bbox.bounds)
-
     def __init__(self, ax,
                  cmap=None,
                  norm=None,
