Lark doesn't run on FIPS enabled systems on older versions of python 3 #1250
Description
Describe the bug
Due to md5 ciphers being disabled on FIPS enabled systems, Lark won't work due to the md5_digest method in the load_grammer module. On Python 3.9 and up this will work, but not all users running FIPS are on 3.9 and since Lark purports to support python as low as 3.6, we should probably make the module FIPS compliant by simply removing MD5 hashing. This change would build on the work already put into place by #1187
To Reproduce
On a RHEL 7 system running Python 3.6, when opening a grammar file with lark_parser = Lark.open(GRAMMAR_FILE), I get the following error (note that the top of the stack is redacted):
...
File "/usr/lib/python3.6/site-packages/lark/lark.py", line 567, in open
return cls(f, **options)
File "/usr/lib/python3.6/site-packages/lark/lark.py", line 349, in __init__
self.grammar, used_files = load_grammar(grammar, self.source_path, self.options.import_paths, self.options.keep_all_tokens)
File "/usr/lib/python3.6/site-packages/lark/load_grammar.py", line 1410, in load_grammar
builder.load_grammar(grammar, source)
File "/usr/lib/python3.6/site-packages/lark/load_grammar.py", line 1250, in load_grammar
self.do_import(dotted_path, base_path, aliases, mangle)
File "/usr/lib/python3.6/site-packages/lark/load_grammar.py", line 1317, in do_import
h = md5_digest(text)
File "/usr/lib/python3.6/site-packages/lark/load_grammar.py", line 1423, in md5_digest
return hashlib.md5(s.encode('utf8')).hexdigest()
ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for fips