gdb/testsuite: use "is" for type comparison in Python files

Fix flake8 warnings like:

    gdb/testsuite/gdb.python/py-unwind.py:253:20: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`

Change-Id: I506c0874bba88aa418757d94168992bf4ec677f8
Approved-By: Tom Tromey <tom@tromey.com>

gdb/testsuite/gdb.python/py-missing-objfile.py

@@ -41,10 +41,10 @@ handler_last_filename = None
 # A helper function that makes some assertions about the arguments
 # passed to a MissingObjfileHandler.__call__() method.
 def check_args(pspace, buildid, filename):
-    assert type(filename) == str
+    assert type(filename) is str
     assert filename != ""
-    assert type(pspace) == gdb.Progspace
-    assert type(buildid) == str
+    assert type(pspace) is gdb.Progspace
+    assert type(buildid) is str
     assert buildid != ""
 
 

gdb/testsuite/gdb.python/py-unwind.py

@@ -250,7 +250,7 @@ class validating_unwinder(Unwinder):
 
         for key, value in info.items():
             assert key in old_info, key + " not in old_info"
-            assert type(value) == type(old_info[key])
+            assert type(value) is type(old_info[key])
             if isinstance(value, gdb.Block):
                 assert value.start == old_info[key].start
                 assert value.end == old_info[key].end

gdb/testsuite/gdb.python/source2.py

@@ -16,6 +16,6 @@
 #  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 # Make sure __file__ is defined.
-assert type(__file__) == str
+assert type(__file__) is str
 
 print("y%ss" % "e")