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


toolchain-utils/crosperf/flag_test_unittest.py
************* Module flag_test_unittest
R:  1, 0: Shebang should be #!/usr/bin/python2 or #!/usr/bin/python3 (bad-shebang)
C:  1, 0: Modules should have docstrings (even a one liner) (module-missing-docstring)
C: 10, 0: Classes should have docstrings (even a one liner) (class-missing-docstring)
W: 15,25: Access to a protected member _is_test of a client class (protected-access)
W: 16,25: Access to a protected member _is_test of a client class (protected-access)
W: 33,25: Access to a protected member _is_test of a client class (protected-access)
W: 34,25: Access to a protected member _is_test of a client class (protected-access)
R:  1, 0: Missing "from __future__ import print_function" line (missing-print-function)

toolchain-utils/crosperf/experiment_file_unittest.py
************* Module experiment_file_unittest
R:  1, 0: Shebang should be #!/usr/bin/python2 or #!/usr/bin/python3 (bad-shebang)
C:  1, 0: Modules should have docstrings (even a one liner) (module-missing-docstring)
C: 86, 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)


toolchain-utils/crosperf/experiment_file.py
************* Module experiment_file
C:  1, 0: Modules should have docstrings (even a one liner) (module-missing-docstring)
W:  8, 0: Unused Settings imported from settings (unused-import)
R:  1, 0: Missing "from __future__ import print_function" line (missing-print-function)