title: I received an error message while trying to install datatable in python 3.7.4 using python -m pip install datatable
body: <p>When I tried to install a datatable using <code>pythom -m pip install datatable</code> in python 3.7.4, I received the following error message:
   Complete output (26 lines):</p>
  
  <pre><code>Start setup.py
    command = `install`
  
  Find an LLVM installation
    Environment variable LLVM is not set
    Environment variable LLVM7 is not set
    Environment variable LLVM6 is not set
    Environment variable LLVM5 is not set
    Environment variable LLVM4 is not set
    Candidate directory `/usr/local/opt/llvm` not found
    The build will proceed without Llvm support
  
  Determine the compiler
    Environment variable `CXX` is not set
    Environment variable `CC` is not set
    Llvm installation not found, cannot search for the clang++ compiler
    'compiler_cxx'
    Compiler `clang++.exe` is not found
    Compiler `gcc.exe` is not found
  
  Prepare the environment
  
  
  SystemExit: Suitable C++ compiler cannot be determined. Please specify a compiler executable in the `CXX` environment variable.
  
  ----------------------------------------
  ERROR: Command errored out with exit status 1: 'C:\Users\Kazerooni\AppData\Local\Programs\Python\Python37-32\python.exe' -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'C:\\Users\\KAZERO~1\\AppData\\Local\\Temp\\pip-install-v4t9g3f2\\datatable\\setup.py'"'"'; __file__='"'"'C:\\Users\\KAZERO~1\\AppData\\Local\\Temp\\pip-install-v4t9g3f2\\datatable\\setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record 'C:\Users\KAZERO~1\AppData\Local\Temp\pip-record-tjfm4gd6\install-record.txt' --single-version-externally-managed --compile Check the logs for full command output.
  </code></pre>