fix vcf filter and tweak test_imports for better pythonic

gramps/plugins/test/test_exports.py

@@ -148,7 +148,16 @@ def vcffilt(line):
     The differences are not functional, but are related to changes in Gramps
     version.
     """
-    return False if line.startswith('PRODID:') else True
+    diftyp = line[0]
+    if diftyp == '@':
+        retval = False
+    elif diftyp == ' ':
+        retval = False
+    elif 'PRODID:' in line:  # Gramps version is on these lines
+        retval = False
+    else:
+        retval = True
+    return retval
 
 
 class ExportControl(unittest.TestCase):

gramps/plugins/test/test_imports.py

@@ -243,7 +243,7 @@ else:
     _tstfiles = []
     for _tstfile in os.listdir(TEST_DIR):
         (fname, ext) = os.path.splitext(os.path.basename(_tstfile))
-        if ext == ".gramps" or ext == ".difs" or ext == ".bak" \
+        if ext in (".gramps", ".difs", ".bak") \
                 or not fname.startswith("imp_"):
             continue
         test_func = make_tst_function(_tstfile, fname)