Fix get_catmaid_papers.py token error

[dosumis]

./get_catmaid_papers.py
Traceback (most recent call last):
  File "./get_catmaid_papers.py", line 153, in <module>
    gen_cat_skid_report("https://l1em.catmaid.virtualflybrain.org", 1, "papers", 
"L1EM").to_csv("../VFB_reporting_results/EM_CATMAID_L1_skids.tsv", sep="\t", index=False)
  File "./get_catmaid_papers.py", line 52, in gen_cat_skid_report
    csrftoken = client.cookies[csrf_key]
UnboundLocalError: local variable 'csrf_key' referenced before assignment

[dosumis]

DataBase down. SHould be working once up.

But - should also edit code to => more informative error message