Instrument Python version metric

python/lib/dependabot/python/file_fetcher.rb

@@ -37,6 +37,28 @@ def self.required_files_message
           "or a Pipfile."
       end
 
+      def ecosystem_versions
+        # Hmm... it's weird that this calls file parser methods, but here we are in the file fetcher... for all
+        # ecosystems our goal is to extract the user specified versions, so we'll need to do file parsing... so should
+        # we move this `ecosystem_versions` metrics method to run in the file parser for all ecosystems? Downside is if
+        # file parsing blows up, this metric isn't emitted, but reality is we have to parse anyway... as we want to know
+        # the user-specified range of versions, not the version Dependabot chose to run.
+        python_requirement_parser = FileParser::PythonRequirementParser.new(dependency_files: files)
+        language_version_manager = LanguageVersionManager.new(python_requirement_parser: python_requirement_parser)
+        {
+          languages: {
+            python: {
+              # TODO: alternatively this could use `python_requirement_parser.user_specified_requirements` which
+              # returns an array... which we could flip to return a hash of manifest name => version
+              # string and then check for min/max versions... today it simply defaults to
+              # array.first which seems rather arbitrary.
+              "raw" => language_version_manager.user_specified_python_version || "unknown",
+              "max" => language_version_manager.python_major_minor || "unknown"
+            }
+          }
+        }
+      end
+
       private
 
       def fetch_files