Add minimal type review to case_utils

An observed behavior is that mypy will not type signature analysis until
one is added in the call path, e.g. designating `def main() -> None`.
This patch is the minimal set of effects of adding a None return type to
unit test functions.

No further changes needed.  One test not committed is that, before this
patch, this line could be put into a function (I chose the SPARQL
selector's main()) without mypy complaining:

    x : str = 1

After requiring that function return a type, mypy appropriately raised
an error.

References:
* [AC-211] Add static type checking to CASE-Utilities-Python

Signed-off-by: Alex Nelson <alexander.nelson@nist.gov>

Author: ajnelson-nist

case_utils/case_file/__init__.py

@@ -205,7 +205,7 @@ def create_file_node(graph, filepath, node_iri=None, node_prefix=DEFAULT_PREFIX,
 
     return n_file
 
-def main():
+def main() -> None:
     import argparse
     parser = argparse.ArgumentParser()
     parser.add_argument("--base-prefix", default=DEFAULT_PREFIX)

case_utils/case_sparql_construct/__init__.py

@@ -27,7 +27,7 @@
 
 _logger = logging.getLogger(os.path.basename(__file__))
 
-def main():
+def main() -> None:
     parser = argparse.ArgumentParser()
     parser.add_argument("-d", "--debug", action="store_true")
     parser.add_argument("--disallow-empty-results", action="store_true", help="Raise error if no results are returned for query.")

case_utils/case_sparql_select/__init__.py

@@ -42,7 +42,7 @@
 
 _logger = logging.getLogger(os.path.basename(__file__))
 
-def main():
+def main() -> None:
     parser = argparse.ArgumentParser()
     parser.add_argument("-d", "--debug", action="store_true")
     parser.add_argument("--disallow-empty-results", action="store_true", help="Raise error if no results are returned for query.")