Bug: Improve Pyramid exception support in web

[jamoore]

After import

• Improve message
• Display default thumbnail

When opening viewer, display message indicating the time remaining before the image can be viewed:

    try:
        rawPixelsStore.setPixelId(id) # Or anywhere that MissingPyramidException is handld
    except omero.MissingPyramidException, mpe: # Or any omero.ConcurrencyException
        backOffInMillis = mpe.backOff
        backOffInSecs = backOffInMillis / 1000
        self.handleSuggestedBackOff(backOffInSecs)

Need to handle renderingEngine.load() which is called in _prepareRE which is called by _prepareRenderingEngineused in the decorator

@assert_re

which is used by the following methods

• saveDefaults ()
• getDefaultT() & getDefaultZ()
• getT() & getZ() Not sure why re is needed here?
• renderColLinePlotGif() & renderRowLinePlotGif() Not sure why re is needed here?
• createMovie()
• renderJpeg()
• renderJpegRegion()
• getRenderingModel()
• getRenderingModels()
• getChannels()
• _getProjectedThumbnail ()

Currently, if re.load() throws a MissingPyramidException?, it is thrown by _prepareRE but eaten by _prepareRenderingEngine() and image._re is simply None. E.g leading to errors like:

("error in call","Traceback (most recent call last):
  File "/Users/will/Desktop/OMERO/components/tools/OmeroWeb/omeroweb/../omeroweb/webgateway/views.py", line 917, in wrap
    rv = f(request, *args, **kwargs)
  File "/Users/will/Desktop/OMERO/components/tools/OmeroWeb/omeroweb/../omeroweb/webgateway/views.py", line 1119, in imageData_json
    rv = imageMarshal(image, key)
  File "/Users/will/Desktop/OMERO/components/tools/OmeroWeb/omeroweb/../omeroweb/webgateway/views.py", line 1043, in imageMarshal
    tiles = image._re.requiresPixelsPyramid()
AttributeError: 'NoneType' object has no attribute 'requiresPixelsPyramid'
")

See #5534 for Insight ticket