Handle fpocket finding no pockets

If fpocket finds no pockets, it does not
create the output directory, so handle this.

lib/cryptosite/bmi_feature_parser.py

@@ -12,8 +12,12 @@ def get_cnc(apo):
 
     subprocess.check_call(["fpocket", "-f", apo + '.pdb'])
 
-    with open('%s_out/%s_out.pdb' % (apo, apo)) as data:
-        D = data.readlines()
+    try:
+        with open('%s_out/%s_out.pdb' % (apo, apo)) as data:
+            D = data.readlines()
+    except FileNotFoundError:
+        # If fpocket finds no pockets, it does not create the output directory
+        return {}, ('1', '1')
 
     Pockets = {}
     for d in D:

test/input/test-no-pockets.pdb

@@ -0,0 +1 @@
+ATOM    265  O   ILE A  65      -6.422  41.658  49.431  1.00 19.63           O

test/test_bmi_feature_parser.py

@@ -24,6 +24,15 @@ def test_get_cnc(self):
             self.assertEqual(len(res), 8)
             self.assertEqual(num, ('1', '1'))
 
+    def test_get_cnc_no_pockets(self):
+        """Test get_cnc() function with PDB containing no pockets"""
+        with utils.temporary_working_directory():
+            shutil.copy(os.path.join(TOPDIR, 'test', 'input',
+                                     'test-no-pockets.pdb'), '1abc.pdb')
+            res, num = bmi_feature_parser.get_cnc('1abc')
+            self.assertEqual(len(res), 0)
+            self.assertEqual(num, ('1', '1'))
+
     def test_get_cnc_pockets(self):
         """Test get_cnc() parsing of pocket information"""
         with utils.temporary_working_directory():