Merge commit '36bca61764984ff5395653cf8377ec5daa71b709' as 'libs/protobuf'

libs/protobuf/python/README.md

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+Protocol Buffers - Google's data interchange format
+===================================================
+
+Copyright 2008 Google Inc.
+
+This directory contains the Python Protocol Buffers runtime library.
+
+Normally, this directory comes as part of the protobuf package, available
+from:
+
+  https://developers.google.com/protocol-buffers/
+
+The complete package includes the C++ source code, which includes the
+Protocol Compiler (protoc).  If you downloaded this package from PyPI
+or some other Python-specific source, you may have received only the
+Python part of the code.  In this case, you will need to obtain the
+Protocol Compiler from some other source before you can use this
+package.
+
+Development Warning
+===================
+
+The pure python performance is slow. For better performance please
+use python c++ implementation.
+
+Installation
+============
+
+1) Make sure you have Python 3.7 or newer.  If in doubt, run:
+
+       $ python -V
+
+2) Make sure you have Bazel 0.5.4 or later (or CMake 3.5 or later).
+
+3) If you do not have setuptools installed, note that it will be
+   downloaded and installed automatically as soon as you run `setup.py`.
+   If you would rather install it manually, you may do so by following
+   the instructions on [this page](https://packaging.python.org/en/latest/tutorials/installing-packages/).
+
+4) Build the C++ code, or install a binary distribution of `protoc`.  If
+   you install a binary distribution, make sure that it is the same
+   version as this package.  If in doubt, run:
+
+       $ protoc --version
+
+5) Build and run the tests:
+
+       $ python setup.py build
+       $ python setup.py test
+
+   To build, test, and use the C++ implementation, you must first compile
+   `libprotobuf.so` using either [Bazel](../README.md) or [CMake](../src/README.md):
+
+   On OS X:
+
+   If you are running a Homebrew-provided Python, you must make sure another
+   version of protobuf is not already installed, as Homebrew's Python will
+   search `/usr/local/lib` for `libprotobuf.so` before it searches the compiled
+   binaries.
+
+   You can either unlink Homebrew's protobuf or install the `libprotobuf` you
+   built earlier:
+
+       $ brew unlink protobuf
+
+   or
+
+       $ (cd .. && cmake . && make install)
+
+    On other *nix:
+
+    You must make `libprotobuf.so` dynamically available. You can either
+    install libprotobuf you built earlier, or set `LD_LIBRARY_PATH`:
+
+       $ (cd .. && cmake . && make -j20 install)
+
+    or
+
+       $ export LD_LIBRARY_PATH=../bazel-bin
+
+   To build the C++ implementation run:
+
+       $ python setup.py build --cpp_implementation
+
+   Then run the tests like so:
+
+       $ python setup.py test --cpp_implementation
+
+   If some tests fail, this library may not work correctly on your
+   system.  Continue at your own risk.
+
+   Please note that there is a known problem with some versions of
+   Python on Cygwin which causes the tests to fail after printing the
+   error:  `sem_init: Resource temporarily unavailable`.  This appears
+   to be a [bug either in Cygwin or in
+   Python](http://www.cygwin.com/ml/cygwin/2005-07/msg01378.html).
+
+   We do not know if or when it might be fixed.  We also do not know
+   how likely it is that this bug will affect users in practice.
+
+6) Install:
+
+       $ python setup.py install
+
+   or:
+
+       $ (cd .. && make install)
+       $ python setup.py install --cpp_implementation
+
+   This step may require superuser privileges.
+   NOTE: To use C++ implementation, you need to export an environment
+   variable before running your program.  See the "C++ Implementation"
+   section below for more details.
+
+Usage
+=====
+
+The complete documentation for Protocol Buffers is available via the
+web at:
+
+  https://developers.google.com/protocol-buffers/
+
+C++ Implementation
+==================
+
+The C++ implementation for Python messages is built as a Python extension to
+improve the overall protobuf Python performance.
+
+To use the C++ implementation, you need to install the C++ protobuf runtime
+library, please see instructions in the parent directory.