SNLite node depends on context

Created by: portnov

I programmatically load node tree and try to export it. The code is in the "testing" branch: https://github.com/nortikin/sverchok/pull/2011/files#diff-2594045266f6e0898d61c2674cb78b0dR8

Basically what the code does is:

# Link the whole node tree from reference blend file. link=True or False does not matter.
    with bpy.data.libraries.load(reference_blend_path, link=True) as (data_src, data_dst):
        data_dst.node_groups = ["TestingTree"]

# Obtain linked node tree
tree = bpy.data.node_groups["TestingTree"]

# Export it
export_result = create_dict_of_tree(tree)

Here is the blend file which I am loading: script_uv_ref.blend.gz

And this is what I receive:

ERROR: test_script_uv_export (tree_export_tests.ScriptUvExportTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/portnov/.config/blender/2.79/scripts/addons/sverchok-master/tests/tree_export_tests.py", line 13, in test_script_uv_export
    export_result = create_dict_of_tree(self.tree)
  File "/home/portnov/.config/blender/2.79/scripts/addons/sverchok-master/utils/sv_IO_panel_tools.py", line 298, in create_dict_of_tree
    node.storage_get_data(node_dict)
  File "/home/portnov/.config/blender/2.79/scripts/addons/sverchok-master/nodes/generator/script1_lite.py", line 493, in storage_get_data
    storage = self.node_dict[hash(self)]['sockets']
KeyError: -9223363294578807616

It looks like self.node_dict is called depending on current bpy.context somehow.

Found while testing #2011 .