Catch missing imports and errors like #1520 and #1521
__E901,E999,F821,F822,F823__ are the "_showstopper_" [flake8](http://flake8.pycqa.org) issues that can halt the runtime with a SyntaxError, NameError, etc. Most other flake8 issues are merely "style violations" -- useful for readability but they do not effect runtime safety.
* F821: undefined name `name`
* F822: undefined name `name` in `__all__`
* F823: local variable name referenced before assignment
* E901: SyntaxError or IndentationError
* E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree
In Python 3, __reload()__ was moved and __sys.setdefaultencoding()__ because the default is already utf-8. Also __Error()__ is an _undefined name_ and __Exception()__ creates a generic exception.
Was good idea, but with C++ types with constructor/destructor, was getting in
the way as compiler was destructing those items where it was not desired.
Since C++ does not allow zero-sized arrays, just remove it...
* reimplement ByteStr as byte_str_t based on hb_ubytes_t
Unuse start_embed<ByteStr>
Also renamed SubByteStr to byte_str_ref_t
More renaming to come
* substr renamed to str_ref in line with its type byte_str_ref_t
* uncamelize non-table struct names
* uncamelized non-struct types OpCode etc
* add byte_str_t copy ctor
* test
* test2
* undo tests
* fix bot failure
* undo the previous change
* fixed tabs, added inline
* Revert "fixed tabs, added inline"
This reverts commit 21163c30e9d18759414f7fe2518628241599f039.
* fix tabs
To fix older compilers again (this was the case in hb_array_t).
hb-ot-layout-common.hh:1353: note: candidate 2: operator[](T*, int) <built-in>
hb-ot-layout-common.hh:1354: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-iter.hh:63: note: candidate 1: Item& hb_iter_t<Iter, Item>::operator[](unsigned int) const [with Iter = hb_array_t<const OT::IntType<short unsigned int, 2u> >, Item = const OT::IntType<short unsigned int, 2u>]
hb-ot-layout-common.hh:1354: note: candidate 2: operator[](T*, int) <built-in>
hb-ot-layout-common.hh: In member function 'bool OT::ClassDef::serialize(hb_serialize_context_t*, hb_array_t<const OT::IntType<short unsigned int, 2u> >, hb_array_t<const OT::IntType<short unsigned int, 2u> >)':
hb-ot-layout-common.hh:1490: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-iter.hh:63: note: candidate 1: Item& hb_iter_t<Iter, Item>::operator[](unsigned int) const [with Iter = hb_array_t<const OT::IntType<short unsigned int, 2u> >, Item = const OT::IntType<short unsigned int, 2u>]
hb-ot-layout-common.hh:1490: note: candidate 2: operator[](T*, int) <built-in>
