static code analysis: make it pass flake8 3.7.4 (!1748)

Test with flake8: *.py
./test/check_checksums.py:13:13: E117 over-indented
./pmb/config/init.py:97:8: F632 use ==/!= to compare str, bytes, and int literals
./pmb/parse/arguments.py:229:13: E117 over-indented

pmb/config/init.py

@@ -94,7 +94,7 @@ def ask_for_keymaps(args, device):
     options = info["keymaps"].split(' ')
     logging.info("Available keymaps for device (" + str(len(options)) +
                  "): " + ", ".join(options))
-    if args.keymap is "":
+    if args.keymap == "":
         args.keymap = options[0]
 
     while True:

pmb/parse/arguments.py

@@ -226,7 +226,7 @@ def arguments_kconfig(subparser):
     check.add_argument("--arch", choices=arch_choices, dest="arch")
     check_package = check.add_argument("package", default="", nargs='?')
     if argcomplete:
-            check_package.completer = kernel_completer
+        check_package.completer = kernel_completer
 
     # "pmbootstrap kconfig edit"
     edit = sub.add_parser("edit", help="edit kernel aport config")

test/check_checksums.py

@@ -10,8 +10,8 @@ def get_changed_files():
         raw = subprocess.check_output(['git', 'diff', '--name-only',
                                        'master...{}'.format(branch)])
     except (KeyError, subprocess.CalledProcessError):
-            raw = subprocess.check_output(['git', 'diff', '--name-only',
-                                           'HEAD~1'])
+        raw = subprocess.check_output(['git', 'diff', '--name-only',
+                                       'HEAD~1'])
     return raw.decode().splitlines()