Please fix the following 'cros lint' errors in toolchain-utils:

toolchain-utils/crosperf/machine_image_manager.py
************* Module machine_image_manager
C:  1, 0: Modules should have docstrings (even a one liner) (module-missing-docstring)
W:146,25: Unused variable 'd' (unused-variable)
C:193, 2: Section names should be "Args:", "Returns:", "Yields:", and "Raises:": offset:2: {        Arguments:} (docstring-section-name)
W:218,29: Access to a protected member _label_brl_map of a client class (protected-access)
W:272,11: Unused variable 'l' (unused-variable)
W:280,11: Unused variable 'd' (unused-variable)
C:283, 2: Leading whitespace in docstring (excess or missing): offset:0: { Search matrix for d with N. } (docstring-leading-whitespace)
C:283, 2: Trailing whitespace in docstring: offset:1: { Search matrix for d with N. } (docstring-trailing-whitespace)

../work/toolchain-utils/crosperf/download_images.py
************* Module download_images
C:  1, 0: Modules should have docstrings (even a one liner) (module-missing-docstring)
E: 10, 0: No name 'command_executer' in module 'utils' (no-name-in-module)
C: 17, 0: Classes should have docstrings (even a one liner) (class-missing-docstring)
W: 31, 4: Unused variable 'retval' (unused-variable)
R:  1, 0: Missing "from __future__ import print_function" line (missing-print-function)


../work/toolchain-utils/crosperf/results_organizer_unittest.py
************* Module results_organizer_unittest
R:  1, 0: Shebang should be #!/usr/bin/python2 or #!/usr/bin/python3 (bad-shebang)
C:  1, 0: Second line should be blank (docstring-second-line-blank)
C:  1, 0: Closing triple quotes should not be cuddled (docstring-cuddled-quotes)
C: 69, 0: Classes should have docstrings (even a one liner) (class-missing-docstring)
R:  1, 0: Missing "from __future__ import print_function" line (missing-print-function)