Fix the error below by adding the package path to `PATH`:

    * DONE (exNSS4)
    Loading required package: exNSS4
    building package exSexpr ...
    Converting Rd files to LaTeX
    Error in texi2dvi(file = file, pdf = TRUE, clean = clean, quiet = quiet,  :
      Running 'texi2dvi' on 'Rd2.tex' failed.
    Messages:
    You don't have a working TeX binary (tex) installed anywhere in
    your PATH, and texi2dvi cannot proceed without one.  If you want to use
    this script, you'll need to install TeX (if you don't have it) or change
    your PATH or TEX environment variable (if you do).  See the --help
    output for more details.

    For information about obtaining TeX, please see http://tug.org/texlive,
    or do a web search for TeX and your operating system or distro.
    Output:

    Error in texi2dvi(file = file, pdf = TRUE, clean = clean, quiet = quiet,  :
      Running 'texi2dvi' on 'Rd2.tex' failed.
    Messages:
    You don't have a working TeX binary (tex) installed anywhere in
    your PATH, and texi2dvi cannot proceed without one.  If you want to use
    this script, you'll need to install TeX (if you don't have it) or change
    your PATH or TEX environment variable (if you do).  See the --help
    output for more details.

    For information about obtaining TeX, please see http://tug.org/texlive,
    or do a web search for TeX and your operating system or distro.
    Output:

    Error in running tools::texi2pdf()
    * checking for file '/dev/shm/R-3.6.0-0.build.tmp/RtmpR8JydU/Pkgs/exSexpr/DESCRIPTION' ... OK
    * preparing 'exSexpr':
    * checking DESCRIPTION meta-information ... OK
    * installing the package to process help pages
    * saving partial Rd database
    * building the PDF package manual
    Hmm ... looks like a package
    Creating pdf output from LaTeX ...
    Error: R CMD build failed (no tarball) for package exSexpr

The errors below are in the build log.

    $ grep ^Error R-3.6.0-0.build.log
    Error: package ‘S4Vectors’ 0.18.3 was found, but >= 0.19.11 is required
    by ‘GenomicRanges’
    Error : package ‘S4Vectors’ 0.18.3 is loaded, but >= 0.19.11 is required
    by ‘GenomicRanges’
    Error: loading failed
    Error in reconcilePropertiesAndPrototype(name, slots, prototype,
    superClasses,  :
    Error: unable to load R code in package ‘ensembldb’