human
Solve the following python programming problem given the following code:
def execute_antlr_test(self, expected_package, target_workdir_fun = None) : 
    target = self.get_antlr_target () 
    context = self.create_context () 
    task = self.prepare_execute (context) 
    target_workdir_fun = (target_workdir_fun or (lambda x : safe_mkdtemp (dir = x))) 
    target_workdir = target_workdir_fun (self.build_root) 
    task.execute_codegen (target, target_workdir) 
    syn_target = task._inject_synthetic_target (target, target_workdir) 
    actual_sources = [s for s in Fileset.rglobs ('*.java', root = target_workdir)] 
    expected_sources = syn_target.sources_relative_to_source_root () 
    self.assertEquals (set (expected_sources), set (actual_sources)) 
    def get_package(path) : 
        with open (path) as fp : 
            for line in fp : 
                match = self.PACKAGE_RE.match (line) 
                if match : 
                    return match.group ('package_name') 
return None 
for source in syn_target.sources_relative_to_source_root () : 
        source_path = os.path.join (target_workdir, source) 
        self.assertTrue (os.path.isfile (source_path), '{0} is not the source root for {1}'.format (target, source)) 
        self.assertEqual (expected_package, get_package (source_path)) 
        self.assertIn (syn_target, context.targets ()) 
return syn_target 

    
    

    Fix the buggy line: self.assertTrue (os.path.isfile (source_path), '{0} is not the source root for {1}'.format (target, source))
assistant
#Here is Python code to fix the buggy line: self.

self.assertTrue (os.path.isfile (source_path), '{0} is not the source root for {1}'.format (target_workdir, source))