chore: fix python lint warnings (#14638)

* chore: fix lint warnings

* chore: another try at python import errors

Looks like the problem is that dbus_mock.py is running as
a script but living in the `lib/` directory where it's part of a
module. Moving it up into the `script/` directory seems to
solve the issue.

script/lib/config.py

@@ -6,10 +6,13 @@ import platform
 import sys
 
 # URL to the mips64el sysroot image.
-MIPS64EL_SYSROOT_URL = 'https://github.com/electron/debian-sysroot-image-creator/releases/download/v0.5.0/debian_jessie_mips64-sysroot.tar.bz2'
+MIPS64EL_SYSROOT_URL = 'https://github.com/electron' \
+                     + '/debian-sysroot-image-creator/releases/download' \
+                     + '/v0.5.0/debian_jessie_mips64-sysroot.tar.bz2'
 # URL to the mips64el toolchain.
 MIPS64EL_GCC = 'gcc-4.8.3-d197-n64-loongson'
-MIPS64EL_GCC_URL = 'http://ftp.loongnix.org/toolchain/gcc/release/' + MIPS64EL_GCC + '.tar.gz'
+MIPS64EL_GCC_URL = 'http://ftp.loongnix.org/toolchain/gcc/release/' \
+                 + MIPS64EL_GCC + '.tar.gz'
 
 BASE_URL = os.getenv('LIBCHROMIUMCONTENT_MIRROR') or \
     'https://s3.amazonaws.com/github-janky-artifacts/libchromiumcontent'
@@ -89,7 +92,8 @@ def get_zip_name(name, version, suffix=''):
 def build_env():
   env = os.environ.copy()
   if get_target_arch() == "mips64el":
-    SOURCE_ROOT = os.path.abspath(os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
+    SOURCE_ROOT = os.path.abspath(os.path.dirname(
+                    os.path.dirname(os.path.dirname(__file__))))
     VENDOR_DIR = os.path.join(SOURCE_ROOT, 'vendor')
     gcc_dir = os.path.join(VENDOR_DIR, MIPS64EL_GCC)
     ldlib_dirs = [