Remove support for cgi.FieldStorage

The python cgi module is being removed in python 3.13[1].

This patch moves the use of cgi.FieldStorage under a try block that will
skip the check for cgi.FieldStorage object in File type parsing.

[1] https://docs.python.org/3/library/cgi.html

Change-Id: Iff145680312c3aba18b5be078fbf1ea32b06080b

wsme/rest/args.py

@@ -1,4 +1,3 @@
-import cgi
 import datetime
 import re
 
@@ -36,8 +35,13 @@ def datetime_from_param(datatype, value):
 
 @from_param.when_object(File)
 def filetype_from_param(datatype, value):
+    # TODO(johnsom) Remove once python 3.13 is the minimum supported version.
+    try:
+        import cgi
         if isinstance(value, cgi.FieldStorage):
             return File(fieldstorage=value)
+    except ImportError:
+        pass
     return File(content=value)