typing: constrain argument/return types of encoding.toutf8b()

typing: fix argument type of encoding.tolocal() and .fromutf8b() Fixes various pytype errors.

typing: fix forward reference in _Tlocalstr type bound AFAIK, a quoted string in type position is translated to its ForwardRef. https://github.com/python/typing/issues/34 This fixes the following error: File "mercurial/encoding.py", line 38, in <module>: Name 'localstr' is not defined [name-error]

encoding: make getcols() raise exception explicitly This helps pytype. File "mercurial/encoding.py", line 329, in getcols: bad option in return type [bad-return-type] Expected: bytes Actually returned: None

setup: conditionalize access to `sys.dllhandle` when building extensions This code is only run on Windows, and was crashing PyOxidizer when running in `setup-py-install` mode. Now an oxidized binary can be built by simply pointing to setup.py. Something is slightly different now that it's not being built from a virtualenv. Previously, `hg version` could print to the screen, but now it aborts saying "Incorrect function". But I can see the output if redirected to a file, and it's not complaining about missing C extensions, so I think those are loading now (unlike from the virtualenv). The interesting this about this incorrect function output is that it failed when initially built. I then went back and did a `make clean` and `make local` with py3 and then py2 to ensure I didn't break the existing code. At that point I ran the oxidized executable again and it was able to print to the screen normally! So I ran `pyoxidizer build` again, it only output the following, and then running the executable failed to output again: (pyO2_venv) C:\Users\Matt\hg3\hg_pyO2>pyoxidizer build Finished dev [unoptimized + debuginfo] target(s) in 0.12s packaging application into C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug purging C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug copying C:/Users/Matt/hg3/hg_pyO2\build\target\x86_64-pc-windows-msvc\debug\hg_pyO2.exe to C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug\hg_pyO2.exe resolving packaging state... writing license for [...] hg_pyO2 packaged into C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug executable path: C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug\hg_pyO2.exe Differential Revision: https://phab.mercurial-scm.org/D7444

zeroconf: fix traceback under py3 hg serve under py3 caused struct.error: char format requires a bytes object of length 1 <pulkit25> ah, I think that should be `pycompat.bytechr` instead of chr

setup: use bytes for assumed python version Caught by PyOxidizer when hacking on Windows. # skip-blame for b'' prefixing Differential Revision: https://phab.mercurial-scm.org/D7443