Build failure on Ubuntu 20.04

[cdleary]

Command run:

bazel test -c opt ...

Output:

bazel-out/k8-opt-exec-2B5CBBC6/bin/external/clang_binaries/clang_format: error while loading shared libraries: libtinfo.so.5: cannot open shared object file: No such file or directory

$ ldd bazel-out/k8-opt-exec-2B5CBBC6/bin/external/clang_binaries/clang_format
        linux-vdso.so.1 (0x00007ffdf21f7000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc81e981000)
        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fc81e976000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fc81e970000)
        libtinfo.so.5 => not found
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fc81e821000)
        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fc81e640000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fc81e623000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc81e431000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fc81e9b8000)
$ locate libtinfo
...
/snap/core18/1705/lib/x86_64-linux-gnu/libtinfo.so.5
/snap/core18/1705/lib/x86_64-linux-gnu/libtinfo.so.5.9
...
/usr/lib/x86_64-linux-gnu/libtinfo.so.6
/usr/lib/x86_64-linux-gnu/libtinfo.so.6.2
...
$ dpkg --list | grep libtinfo
ii  libtinfo6:amd64                            6.2-0ubuntu2                               amd64        shared low-level terminfo library for terminal handling
$ apt-cache search libtinfo
libncurses-dev - developer's libraries for ncurses
libtinfo-dev - transitional package for libncurses-dev
libtinfo6 - shared low-level terminfo library for terminal handling
libtinfo5 - shared low-level terminfo library (legacy version)

So we likely need to update the installation instructions to tell users to install libtinfo5 given the current clang-format binary build, this issue serves as a reminder.

[cdleary]

Users will also have to symlink python3 to python somewhere on their PATH because the py_binary script uses #!/usr/bin/env python and Ubuntu 20.04 eliminates python from the $PATH in favor of the more explicit python3 -- looks like bazelbuild/bazel#8685 is tracking a Bazel-level solution.

[cdleary]

Also just a note for installation instructions, have to include:

apt install python3-numpy python3-scipy python3-termcolor python3-psutil

[cdleary]

I also needed the attached changes to build on Ubuntu 20.04
xls-ubuntu-20.diff.txt

[cdleary]

Confirmed fixed by 5b23276

Also notable we may be able to switch some of our Python dependencies to pip-based ones now that we use the pip support in Bazel's "python rules".