--- a/build/moz.configure/android-ndk.configure
+++ b/build/moz.configure/android-ndk.configure
@@ -49,17 +49,17 @@ def ndk(value, build_project):
     if value:
         return value[0]
 
 set_config('ANDROID_NDK', ndk)
 add_old_configure_assignment('android_ndk', ndk)
 
 @depends(target, android_version, ndk)
 @checking('for android platform directory')
-@imports('os')
+@imports(_from='os.path', _import='isdir')
 def android_platform(target, android_version, ndk):
     if target.os != 'Android':
         return
 
     if 'mips' in target.cpu:
         target_dir_name = 'mips'
     elif 'aarch64' == target.cpu:
         target_dir_name = 'arm64'
@@ -75,17 +75,17 @@ def android_platform(target, android_ver
     else:
         platform_version = android_version
 
     platform_dir = os.path.join(ndk,
                                 'platforms',
                                 'android-%s' % platform_version,
                                 'arch-%s' % target_dir_name)
 
-    if not os.path.isdir(platform_dir):
+    if not isdir(platform_dir):
         die("Android platform directory not found. With the current "
             "configuration, it should be in %s" % platform_dir)
 
     return platform_dir
 
 add_old_configure_assignment('android_platform', android_platform)
 
 @depends(android_platform)
@@ -93,17 +93,17 @@ def extra_toolchain_flags(platform_dir):
     if not platform_dir:
         return []
     return ['-idirafter',
             os.path.join(platform_dir, 'usr', 'include')]
 
 @depends(target, host, ndk, '--with-android-toolchain',
          '--with-android-gnu-compiler-version')
 @checking('for the Android toolchain directory', lambda x: x or 'not found')
-@imports('os')
+@imports(_from='os.path', _import='isdir')
 @imports(_from='mozbuild.shellutil', _import='quote')
 def android_toolchain(target, host, ndk, toolchain, gnu_compiler_version):
     if not ndk:
         return
     if toolchain:
         return toolchain[0]
     else:
         if target.cpu == 'arm' and target.endianness == 'little':
@@ -118,21 +118,21 @@ def android_toolchain(target, host, ndk,
             die('Target cpu is not supported.')
 
         toolchain_format = '%s/toolchains/%s-%s/prebuilt/%s-%s'
 
         for version in gnu_compiler_version or ['4.9', '4.8', '4.7']:
             toolchain = toolchain_format % (ndk, target_base, version,
                                             host.kernel.lower(), host.cpu)
             log.debug('Trying %s' % quote(toolchain))
-            if not os.path.isdir(toolchain) and host.cpu == 'x86_64':
+            if not isdir(toolchain) and host.cpu == 'x86_64':
                 toolchain = toolchain_format % (ndk, target_base, version,
                                                 host.kernel.lower(), 'x86')
                 log.debug('Trying %s' % quote(toolchain))
-            if os.path.isdir(toolchain):
+            if isdir(toolchain):
                 return toolchain
         else:
             if gnu_compiler_version:
                 die('Your --with-android-gnu-compiler-version may be wrong')
             die('You have to specify --with-android-toolchain='
                 '/path/to/ndk/toolchain.')
 
 set_config('ANDROID_TOOLCHAIN', android_toolchain)

--- a/build/moz.configure/init.configure
+++ b/build/moz.configure/init.configure
@@ -7,17 +7,17 @@
 include('util.configure')
 include('checks.configure')
 
 option(env='DIST', nargs=1, help='DIST directory')
 
 # Do not allow objdir == srcdir builds.
 # ==============================================================
 @depends('--help', 'DIST')
-@imports('os')
+@imports(_from='os.path', _import='exists')
 def check_build_environment(help, dist):
     topobjdir = os.path.realpath(os.path.abspath('.'))
     topsrcdir = os.path.realpath(os.path.abspath(
         os.path.join(os.path.dirname(__file__), '..', '..')))
 
     if dist:
         dist = normsep(dist[0])
     else:
@@ -42,17 +42,17 @@ def check_build_environment(help, dist):
             '  * If you are building with a mozconfig, you will need to change your\n'
             '  * mozconfig to point to a different object directory.\n'
             '  ***'
         )
 
     # Check for a couple representative files in the source tree
     conflict_files = [
         '*         %s' % f for f in ('Makefile', 'config/autoconf.mk')
-        if os.path.exists(os.path.join(topsrcdir, f))
+        if exists(os.path.join(topsrcdir, f))
     ]
     if conflict_files:
         die('  ***\n'
             '  *   Your source tree contains these files:\n'
             '  %s\n'
             '  *   This indicates that you previously built in the source tree.\n'
             '  *   A source tree build can confuse the separate objdir build.\n'
             '  *\n'
@@ -629,27 +629,27 @@ def default_project(build_env, help):
 option('--enable-project', nargs=1, default=default_project,
        help='Project to build')
 
 option('--with-external-source-dir', env='EXTERNAL_SOURCE_DIR', nargs=1,
        help='External directory containing additional build files')
 
 @depends('--enable-project', '--with-external-source-dir',
          check_build_environment, '--help')
-@imports('os')
+@imports(_from='os.path', _import='exists')
 def include_project_configure(project, external_source_dir, build_env, help):
     if not project:
         die('--enable-project is required.')
 
     base_dir = build_env.topsrcdir
     if external_source_dir:
         base_dir = os.path.join(base_dir, external_source_dir[0])
 
     path = os.path.join(base_dir, project[0], 'moz.configure')
-    if not os.path.exists(path):
+    if not exists(path):
         die('Cannot find project %s', project[0])
     return path
 
 @depends('--with-external-source-dir')
 def external_source_dir(value):
     if value:
         return value[0]
 

--- a/build/moz.configure/old.configure
+++ b/build/moz.configure/old.configure
@@ -10,17 +10,17 @@ def encoded_open(path, mode):
     encoding = 'mbcs' if sys.platform == 'win32' else 'utf-8'
     return codecs.open(path, mode, encoding)
 
 
 option(env='AUTOCONF', nargs=1, help='Path to autoconf 2.13')
 
 @depends(mozconfig, 'AUTOCONF')
 @checking('for autoconf')
-@imports('os')
+@imports(_from='os.path', _import='exists')
 @imports('re')
 def autoconf(mozconfig, autoconf):
     mozconfig_autoconf = None
     if mozconfig['path']:
         make_extra = mozconfig['make_extra']
         if make_extra:
             for assignment in make_extra:
                 m = re.match('(?:export\s+)?AUTOCONF\s*:?=\s*(.+)$',
@@ -46,50 +46,50 @@ def autoconf(mozconfig, autoconf):
             if brew:
                 autoconf = os.path.normpath(os.path.join(
                     brew, '..', '..', 'Cellar', 'autoconf213', '2.13', 'bin',
                     'autoconf213'))
 
     if not autoconf:
         die('Could not find autoconf 2.13')
 
-    if not os.path.exists(autoconf):
+    if not exists(autoconf):
         die('Could not find autoconf 2.13 at %s', autoconf)
 
     return autoconf
 
 set_config('AUTOCONF', autoconf)
 
 
 @depends('OLD_CONFIGURE', mozconfig, autoconf, check_build_environment, shell,
          old_configure_assignments, build_project)
 @imports(_from='__builtin__', _import='open')
 @imports(_from='__builtin__', _import='print')
 @imports('glob')
 @imports('itertools')
-@imports('os')
 @imports('subprocess')
 # Import getmtime without overwriting the sandbox os.path.
 @imports(_from='os.path', _import='getmtime')
+@imports(_from='os.path', _import='exists')
 @imports(_from='mozbuild.shellutil', _import='quote')
 def prepare_configure(old_configure, mozconfig, autoconf, build_env, shell,
                       old_configure_assignments, build_project):
     # os.path.abspath in the sandbox will ensure forward slashes on Windows,
     # which is actually necessary because this path actually ends up literally
     # as $0, and backslashes there breaks autoconf's detection of the source
     # directory.
     old_configure = os.path.abspath(old_configure[0])
     if build_project == 'js':
         old_configure_dir = os.path.dirname(old_configure)
-        if not old_configure_dir.replace(os.sep, '/').endswith('/js/src'):
+        if not old_configure_dir.endswith('/js/src'):
             old_configure = os.path.join(old_configure_dir, 'js', 'src',
                                          os.path.basename(old_configure))
 
     refresh = True
-    if os.path.exists(old_configure):
+    if exists(old_configure):
         mtime = getmtime(old_configure)
         aclocal = os.path.join(build_env.topsrcdir, 'build', 'autoconf',
                                '*.m4')
         for input in itertools.chain(
             (old_configure + '.in',
              os.path.join(os.path.dirname(old_configure), 'aclocal.m4')),
             glob.iglob(aclocal),
         ):

--- a/build/moz.configure/windows.configure
+++ b/build/moz.configure/windows.configure
@@ -260,21 +260,21 @@ def vc_path(c_compiler):
         result = next
         if p.lower() == 'bin':
             break
     return result
 
 
 @depends_win(vc_path)
 @checking('for the Debug Interface Access SDK', lambda x: x or 'not found')
-@imports('os')
+@imports(_from='os.path', _import='isdir')
 def dia_sdk_dir(vc_path):
     if vc_path:
         path = os.path.join(os.path.dirname(vc_path), 'DIA SDK')
-        if os.path.isdir(path):
+        if isdir(path):
             return path
 
 
 @depends_win(vc_path, valid_windows_sdk_dir, valid_ucrt_sdk_dir, dia_sdk_dir)
 @imports('os')
 def include_path(vc_path, windows_sdk_dir, ucrt_sdk_dir, dia_sdk_dir):
     if not vc_path:
         return

--- a/mobile/android/gradle.configure
+++ b/mobile/android/gradle.configure
@@ -16,23 +16,23 @@ option('--with-gradle', nargs='?',
 def with_gradle(value):
     if value:
         return True
 
 set_config('MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE', with_gradle)
 
 
 @depends('--with-gradle', check_build_environment)
-@imports('os')
+@imports(_from='os.path', _import='isfile')
 def gradle(value, build_env):
     gradle = value[0] if len(value) else \
         os.path.join(build_env.topsrcdir, 'gradlew')
 
     # TODO: verify that $GRADLE is executable.
-    if not os.path.isfile(gradle):
+    if not isfile(gradle):
         die('GRADLE must be executable: %s', gradle)
 
     return gradle
 
 set_config('GRADLE', gradle)
 
 
 # Automation uses this to change log levels, not use the daemon, and use

--- a/toolkit/moz.configure
+++ b/toolkit/moz.configure
@@ -87,21 +87,21 @@ include('../js/moz.configure')
 
 
 # L10N
 # ==============================================================
 option('--with-l10n-base', nargs=1, env='L10NBASEDIR',
        help='Path to l10n repositories')
 
 @depends('--with-l10n-base')
-@imports('os')
+@imports(_from='os.path', _import='isdir')
 def l10n_base(value):
     if value:
         path = value[0]
-        if not os.path.isdir(path):
+        if not isdir(path):
             die("Invalid value --with-l10n-base, %s doesn't exist", path)
         return os.path.realpath(os.path.abspath(path))
 
 set_config('L10NBASEDIR', l10n_base)
 
 
 # Default toolkit
 # ==============================================================