without setting the build enviroment, the installation fails with
```
1 error found in build log:
35946 fmtutil [INFO]: /usr/local/pkg/Installs/linux-ubuntu18.04-skylake_avx512/gcc7.4.0/texlive/20190410/rgs2nakycorkgzno/t
exmf-var/web2c/pdftex/pdfcslatex.fmt installed.
35947 fmtutil [INFO]: Disabled formats: 6
35948 fmtutil [INFO]: Successfully rebuilt formats: 45
35949 fmtutil [INFO]: Total formats: 51
35950 fmtutil [INFO]: exiting with status 0
35951 ==> [2020-09-07-21:23:21.482745] '/usr/local/pkg/Installs/linux-ubuntu18.04-skylake_avx512/gcc7.4.0/texlive/20190410/
rgs2nakycorkgzno/bin/x86_64-linux/mtxrun' '--generate'
>> 35952 /usr/bin/env: 'texlua': No such file or directory
```
May be there is a better way...
Cython requires a library that is available in Python 3.8, or before
Python 3.8 with setuptools. This specifies that setuptools is a run
dependency to allow running with Python < 3.8
* new package: py-textblob
add variant to py-nltk to allow for data download/installation
add dependencies to py-nltk so that bin/nltk works
* add resources and resource generation script
At some point in the build phase a script
spack-src/scripts/convert-template
has a shebang looking for python in the path.
Currently this picks up system python if in invoker's path, but should
be using python from spack, so add a build dependency on python.
Many system-installed binaries (at least in Debian) are built against a
libtinfo.so that has versioned symbols. If spack builds a version without this
functionality, and it winds up in the user's LD_LIBRARY_PATH via spack load,
system binaries will begin to complain.
```
$ less log.txt
less: /opt/spack/.../libtinfo.so.6: no version information available (required by less)
```
Co-authored-by: Luke D'Alessandro <ldalessa@uw.edu>
