Issue #62: added try/raise for 'package' attribute to 'system' stanza in JSON export file format

Author: amesar

mlflow_export_import/common/pkg_version.py

@@ -1,7 +1,9 @@
-
-from importlib.metadata import version
+from importlib.metadata import version, PackageNotFoundError
 
 pkg = "mlflow_export_import"
 
 def get_version():
-    return version(pkg)
+    try:
+        return version(pkg)
+    except PackageNotFoundError:
+        return ""