Add pgen module to the Parser folder to produce pgen output using pgen2

Author: pablogsal

Parser/pgen/__init__.py

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+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""The pgen2 package."""

Parser/pgen/__main__.py

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+import os
+import sys
+import argparse
+
+# Make sure we pick the current version of pgen2 (and not whatever is installed)
+CURRENT_FOLDER_LOCATION = os.path.dirname(os.path.realpath(__file__))
+LIB2TO3LOCATION = os.path.realpath(os.path.join(CURRENT_FOLDER_LOCATION,
+                                                '..', '..', 'Lib', 'lib2to3'))
+
+sys.path.insert(0, LIB2TO3LOCATION)
+from pgen2 import pgen
+sys.path.pop(0)
+
+def main(grammar_file, gramminit_h_file, gramminit_c_file, verbose):
+    grammar = pgen.generate_grammar(grammar_file, verbose=verbose)
+    grammar.produce_graminit_h(gramminit_h_file.write)
+    grammar.produce_graminit_c(gramminit_c_file.write)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Parser generator main program.")
+    parser.add_argument(
+        "grammar", type=str, help="The file with the grammar definition in EBNF format"
+    )
+    parser.add_argument(
+        "gramminit_h",
+        type=argparse.FileType('w'),
+        help="The path to write the grammar's non-terminals as #defines",
+    )
+    parser.add_argument(
+        "gramminit_c",
+        type=argparse.FileType('w'),
+        help="The path to write the grammar as initialized data",
+    )
+    parser.add_argument("--verbose", "-v", action="count")
+    args = parser.parse_args()
+    main(args.grammar, args.gramminit_h, args.gramminit_c, args.verbose)