Vocab page fails to load large vocabs

[nicholascar]

VocPrez fails to load large vocabs due to something in the Concept Hierarchy generation code:

  File "/Users/nick/Work/surround/prez/prez/routers/vocprez_router.py", line 88, in scheme_endpoint
    return await scheme(request)
  File "/Users/nick/Work/surround/prez/prez/routers/vocprez_router.py", line 127, in scheme
    return scheme_renderer.render()
  File "/Users/nick/Work/surround/prez/prez/renderers/vocprez/vocprez_scheme_renderer.py", line 211, in render
    return self._render_vocpub(template_context)
  File "/Users/nick/Work/surround/prez/prez/renderers/vocprez/vocprez_scheme_renderer.py", line 162, in _render_vocpub
    return self._render_vocpub_html(template_context)
  File "/Users/nick/Work/surround/prez/prez/renderers/vocprez/vocprez_scheme_renderer.py", line 183, in _render_vocpub_html
    "scheme": self.scheme.to_dict(),
  File "/Users/nick/Work/surround/prez/prez/models/vocprez/vocprez_scheme.py", line 73, in to_dict
    "concepts": self._get_concept_hierarchy(),
  File "/Users/nick/Work/surround/prez/prez/models/vocprez/vocprez_scheme.py", line 201, in _get_concept_hierarchy
    recursive_narrow(top_concept_list, concepts_dict, hierarchy)
  File "/Users/nick/Work/surround/prez/prez/models/vocprez/vocprez_scheme.py", line 190, in recursive_narrow
    "uri": concepts_dict[uri]["uri"],
KeyError: rdflib.term.URIRef('http://pid.geoscience.gov.au/def/voc/ga/countrycode/MNE')

[recalcitrantsupplant]

@jamiefeiss @nicholascar do we have a sufficiently large vocab to test this with?