Fix old style exception raise and exec syntax

Use python 3 compatible exception syntax everywhere

cleanup: pylint, R0123 # (literal-comparison) Comparison to literal

Use predefined constants for PlcStatus instead of string literals

cleanup: pylint, R1704 # (redefined-argument-from-local) Redefining argument with the local name 'Y'

cleanup: pylint, R1701 # (consider-merging-isinstance) Consider merging these isinstance calls to isinstance(CTNLDFLAGS, (str, unicode))

cleanup: pylint, E1304 # (missing-format-string-key) Missing key 'X_name' in format string dictionary

cleanup: pylint, E1300 # (bad-format-character) Unsupported format character '"' (0x22) at index 17

cleanup: pylint, W0111 # (assign-to-new-keyword) Name async will become a keyword in Python 3.7

cleanup: pylint, E1310 (bad-str-strip-call) Suspicious argument in str.strip call

Fix segmentation fault when last lines in text POUs should be highlighted

enable etherlab checks

resort enabled pylint check to move likely-most invasive changes to the end

clean etherlab: pylint, C0330 # (bad-continuation) Wrong hanging indentation before block

clean etherlab: pylint, W0612 # (unused-variable) Unused variable 'X'

clean etherlab: pylint, W1618 # (no-absolute-import) import missing `from __future__ import absolute_import`

clean etherlab: pylint,E0602 # (undefined-variable) Undefined variable 'X'