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Transformation performed by certain fixers (e.g. future, itertools_imports) that causes a statement to be replaced by a blank line will generate a Python file that contains syntax error.
For example, assuming a Python file (foo.py) containing line below:
try:
 from itertools import imap
except ImportError:
 pass
If we run "itertools_imports" fixer against it:
2to3 -f itertools_imports foo.py
will result in the following:
try:
except ImportError:
 pass
which is syntactically incorrect.
Suggestion:
Instead of always replacing such case with BlankLine(), a check should be performed beforehand if the statement to be replaced has any siblings. If no sibling is found, then replace that statement with a "pass" statement instead.
By doing this, Python source files generated by 2to3 are more readily runnable right after the transformation.