Require six for cross Python compatibility. Update imports for Python 3 compatibility.

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extra : rebase_source : 7881f2409e06f68cdb530b89282851e42b7f8d2b
Prefer print_function for Python 3 compatibility

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extra : rebase_source : 7ab911807e66c30fb337aadbaea3345ef7698cc0
extra : histedit_source : aa295836bd90d1e8c35f6bf844e3c195324ad1e9%2C1327cbc6a7ae55b1b5a53ff1e7297fe0a280592f
Update another usage of ConfigParser for Python 3

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extra : rebase_source : d79b615c3d204e5b750a19f5bd198bed80fb4cd4
extra : histedit_source : 3bcd01d501f65d493fd62ccf3835542aaef51734
Use six.moves.range for Python 3 compatibility

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extra : histedit_source : 46fd623bc72c82f75945b85f43710278b5a7968b
Use six for string type detection for improved Python 3 compatibility

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Use six for text type for improved Python 3 compatibility

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