Traceback (most recent call last):
  File "/usr/lib/python3.6/py_compile.py", line 125, in compile
    _optimize=optimize)
  File "<frozen importlib._bootstrap_external>", line 741, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/w/foo.py", line 11
    if f==b-2:
             ^
IndentationError: unindent does not match any outer indentation level

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.6/py_compile.py", line 129, in compile
    raise py_exc
py_compile.PyCompileError: Sorry: IndentationError: unindent does not match any outer indentation level (foo.py, line 11)

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