Fix unit tests which loads data from current dir

Change current dir to the parent dir of the test.

python/tests/test_common.py

@@ -1,4 +1,5 @@
 import unittest
+import os
 
 from hyperon import atoms_are_equivalent
 
@@ -37,6 +38,9 @@ def areEqualMettaRunResults(a, b):
             return False
     return True
 
+def change_dir_to_parent_of(file):
+    os.chdir(os.path.dirname(file))
+
 class HyperonTestCase(unittest.TestCase):
 
     def __init__(self, methodName):

python/tests/test_extend.py

@@ -1,9 +1,13 @@
 import unittest
 
 from hyperon import *
+from test_common import change_dir_to_parent_of
 
 class ExtendTest(unittest.TestCase):
 
+    def setUp(self):
+        change_dir_to_parent_of(__file__)
+
     def test_extend(self):
         '''
         This test verifies that importing from a python-implemnted module along with @register_atoms and @register_tokens works

python/tests/test_load.py

@@ -6,6 +6,9 @@
 
 class LoadAsciiTest(HyperonTestCase):
 
+    def setUp(self):
+        change_dir_to_parent_of(__file__)
+
     def test_load(self):
         metta = MeTTa()
         test_file = "test_load.metta"