gdb/python: fix a few flake8 warnings

Fix these rather obvious warnings reported by flake8:

    ./lib/gdb/FrameIterator.py:16:1: F401 'gdb' imported but unused
    ./lib/gdb/FrameIterator.py:17:1: F401 'itertools' imported but unused
    ./lib/gdb/command/prompt.py:55:26: E712 comparison to False should be 'if cond is False:' or 'if not cond:'
    ./lib/gdb/command/explore.py:526:9: F841 local variable 'has_explorable_fields' is assigned to but never used
    ./lib/gdb/command/explore.py:697:56: E712 comparison to False should be 'if cond is False:' or 'if not cond:'
    ./lib/gdb/command/explore.py:736:62: E712 comparison to False should be 'if cond is False:' or 'if not cond:'
    ./lib/gdb/command/explore.py:767:61: E712 comparison to False should be 'if cond is False:' or 'if not cond:'
    ./lib/gdb/command/frame_filters.py:21:1: F401 'copy' imported but unused
    ./lib/gdb/command/frame_filters.py:22:1: F401 'gdb.FrameIterator.FrameIterator' imported but unused
    ./lib/gdb/command/frame_filters.py:23:1: F401 'gdb.FrameDecorator.FrameDecorator' imported but unused
    ./lib/gdb/command/frame_filters.py:25:1: F401 'itertools' imported but unused
    ./lib/gdb/command/frame_filters.py:179:17: E712 comparison to True should be 'if cond is True:' or 'if cond:'

Change-Id: I4f49c0cb430359ee872222600c61d9c5283b09ab

gdb/python/lib/gdb/FrameIterator.py

@@ -13,9 +13,6 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-import gdb
-import itertools
-
 
 class FrameIterator(object):
     """A gdb.Frame iterator.  Iterates over gdb.Frames or objects that

gdb/python/lib/gdb/command/explore.py

@@ -523,7 +523,6 @@ class CompoundExplorer(object):
         else:
             print("'%s' is a %s with the following " "fields:\n" % (name, type_desc))
 
-        has_explorable_fields = False
         current_choice = 0
         choice_to_compound_field_map = {}
         print_list = []
@@ -694,7 +693,7 @@ class ExploreCommand(gdb.Command):
         )
 
     def invoke(self, arg_str, from_tty):
-        if ExploreUtils.check_args("explore", arg_str) == False:
+        if ExploreUtils.check_args("explore", arg_str) is False:
             return
 
         # Check if it is a value
@@ -733,7 +732,7 @@ class ExploreValueCommand(gdb.Command):
         )
 
     def invoke(self, arg_str, from_tty):
-        if ExploreUtils.check_args("explore value", arg_str) == False:
+        if ExploreUtils.check_args("explore value", arg_str) is False:
             return
 
         value = ExploreUtils.get_value_from_str(arg_str)
@@ -764,7 +763,7 @@ class ExploreTypeCommand(gdb.Command):
         )
 
     def invoke(self, arg_str, from_tty):
-        if ExploreUtils.check_args("explore type", arg_str) == False:
+        if ExploreUtils.check_args("explore type", arg_str) is False:
             return
 
         datatype = ExploreUtils.get_type_from_str(arg_str)

gdb/python/lib/gdb/command/frame_filters.py

@@ -18,11 +18,7 @@
 
 import sys
 import gdb
-import copy
-from gdb.FrameIterator import FrameIterator
-from gdb.FrameDecorator import FrameDecorator
 import gdb.frames
-import itertools
 
 # GDB Commands.
 class SetFilterPrefixCmd(gdb.Command):
@@ -176,7 +172,7 @@ def _complete_frame_filter_list(text, word, all_flag):
         from text/word analysis.  This list can be empty when there
         are no suggestions for completion.
     """
-    if all_flag == True:
+    if all_flag:
         filter_locations = ["all", "global", "progspace"]
     else:
         filter_locations = ["global", "progspace"]

gdb/python/lib/gdb/command/prompt.py

@@ -52,7 +52,7 @@ class _ExtendedPrompt(gdb.Parameter):
             return "The extended prompt is not set."
 
     def get_set_string(self):
-        if self.hook_set == False:
+        if self.hook_set is False:
             gdb.prompt_hook = self.before_prompt_hook
             self.hook_set = True
         return ""