geteventhist sometimes generates an obscure error.

[mhearne-usgs]

Describe the bug
geteventhist us60003sc0 -d ~/tmp -f excel

results in this error message:

Failed to retrieve event history data for
        event us60003sc0. Error message is as follows. Exiting.
        "'contents'"

To Reproduce
geteventhist us60003sc0 -d ~/tmp -f excel

Expected behavior
A file should have been generated.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

      active environment : comcat
    active env location : /Users/mhearne/miniconda/envs/comcat
            shell level : 2
       user config file : /Users/mhearne/.condarc
 populated config files : /Users/mhearne/.condarc
          conda version : 4.8.1
    conda-build version : not installed
         python version : 3.7.3.final.0
       virtual packages : __osx=10.13.6
       base environment : /Users/mhearne/miniconda  (writable)
           channel URLs : https://conda.anaconda.org/conda-forge/osx-64
                          https://conda.anaconda.org/conda-forge/noarch
                          https://repo.anaconda.com/pkgs/main/osx-64
                          https://repo.anaconda.com/pkgs/main/noarch
                          https://repo.anaconda.com/pkgs/r/osx-64
                          https://repo.anaconda.com/pkgs/r/noarch
          package cache : /Users/mhearne/miniconda/pkgs
                          /Users/mhearne/.conda/pkgs
       envs directories : /Users/mhearne/miniconda/envs
                          /Users/mhearne/.conda/envs
               platform : osx-64
             user-agent : conda/4.8.1 requests/2.22.0 CPython/3.7.3 Darwin/17.7.0 OSX/10.13.6
                UID:GID : 176300529:176300529
             netrc file : None
           offline mode : False