Fix bug in test

Author: ezralanglois

src/ext/python/core.py

@@ -775,12 +775,6 @@ def read(run, valid_to_load=None, requires=None, search_paths=None, **extra):
     ...
     interop.py_interop_run.xml_file_not_found_exception: cannot open file some/non/existing/run_folder_name/RunInfo.xml
 
-    Read from a None object
-    >>> metrics = read("")
-    Traceback (most recent call last):
-    ...
-    ValueError: invalid null reference in method 'run_metrics_read', argument 2 of type 'std::string const &'
-
     :param run: string path including name of run folder (or run_metrics object)
     :param valid_to_load: list of strings containing InterOp metric names (Default: None, load everything)
     :param requires: list of required metric (Default: None, check nothing)