title: Issue for Python RAWPY package installation on Windows
body: <p>I want to read RAW files on Python, and it seems that the Rawpy package is well suited for this. However when trying to install it using the Windows CMD</p>
  
  <pre><code>C:\Users\myself&gt;py -m pip install rawpy
  </code></pre>
  
  <p>Or directly using Spyder command line with</p>
  
  <pre><code>!pip install rawpy
  </code></pre>
  
  <p>I get the following error</p>
  
  <pre><code>Using cached https://files.pythonhosted.org/packages/67/05/866890cb4d0d76f12bf83cc55a935694c9febb4728cca861d3f7711f46f4/rawpy-0.12.0.tar.gz
  Requirement already satisfied: numpy in c:\users\myself\appdata\local\continuum\anaconda3\lib\site-packages (from rawpy) (1.15.1)
  Building wheels for collected packages: rawpy
    Running setup.py bdist_wheel for rawpy ... error
    Complete output from command C:\Users\myself\AppData\Local\Continuum\anaconda3\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\myself\\AppData\\Local\\Temp\\pip-install-40sfkvpi\\rawpy\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d C:\Users\myself\AppData\Local\Temp\pip-wheel-3bs1uw1y --python-tag cp37:
    LibRaw git submodule is not cloned yet, will invoke "git submodule update --init" now
    copying CMake scripts from LibRaw-cmake repository
    Traceback (most recent call last):
      File "&lt;string&gt;", line 1, in &lt;module&gt;
      File "C:\Users\myself\AppData\Local\Temp\pip-install-40sfkvpi\rawpy\setup.py", line 298, in &lt;module&gt;
        windows_libraw_compile()
      File "C:\Users\myself\AppData\Local\Temp\pip-install-40sfkvpi\rawpy\setup.py", line 151, in windows_libraw_compile
        clone_submodules()
      File "C:\Users\myself\AppData\Local\Temp\pip-install-40sfkvpi\rawpy\setup.py", line 132, in clone_submodules
        shutil.copy('external/LibRaw-cmake/CMakeLists.txt', 'external/LibRaw/CMakeLists.txt')
      File "C:\Users\myself\AppData\Local\Continuum\anaconda3\lib\shutil.py", line 241, in copy
        copyfile(src, dst, follow_symlinks=follow_symlinks)
      File "C:\Users\myself\AppData\Local\Continuum\anaconda3\lib\shutil.py", line 120, in copyfile
        with open(src, 'rb') as fsrc:
    FileNotFoundError: [Errno 2] No such file or directory: 'external/LibRaw-cmake/CMakeLists.txt'
  </code></pre>
  
  <p>The last error line explicitly says that the file <em>external/LibRaw-cmake/CMakeLists.txt</em> cannot be found. Do you have any idea how to solve the issue?</p>
  
  <p>For information, other packages don't show errors when running these CMD command lines. The error is really <em>rawpy</em> package dependent.</p>