title: Pyinstaller is missing modulename._modulename
body: <p>I'm using pyinstaller to build an <code>.exe</code> file on windows including a QT GUI and some image read and write functions. In my main python file, I do <code>import tifffile</code> for reading <code>.tiff</code> images. Pyinstaller compiles my project without errors. When I run it, I get a warning in my terminal saying:</p>
  
  <p><code>path_to_my_project\tifffile\tiffffile.py:8211: UserWarning: No module named 'tifffile._tifffile' Functionality might be degraded or be slow.</code></p>
  
  <p>However, I can use the parts of my app that use the corresponding functions from the <code>tifffile</code> module. My question now is, how I can fix this or if it's save to ignore, how to suppress the warning.</p>
  
  <p>That's the conda environment I'm using if of any importance:</p>
  
  <pre><code>altgraph                  0.16.1                   pypi_0    pypi
  blas                      1.0                         mkl
  ca-certificates           2019.5.15                     1
  certifi                   2019.6.16                py37_1
  dc-imgproc                1.1.1                    pypi_0    pypi
  future                    0.17.1                   pypi_0    pypi
  hdf5                      1.8.20               hac2f561_1
  icc_rt                    2019.0.0             h0cc432a_1
  icu                       58.2                 ha66f8fd_1
  intel-openmp              2019.5                      281
  jpeg                      9b                   hb83a4c4_2
  libopencv                 3.4.2                h20b85fd_0
  libpng                    1.6.37               h2a8f88b_0
  libtiff                   4.0.10               hb898794_2
  macholib                  1.11                     pypi_0    pypi
  mkl                       2019.5                      281
  mkl-service               2.3.0            py37hb782905_0
  mkl_fft                   1.0.14           py37h14836fe_0
  mkl_random                1.0.2            py37h343c172_0
  numpy                     1.16.5           py37h19fb1c0_0
  numpy-base                1.16.5           py37hc3f5095_0
  opencv                    3.4.2            py37h40b0b35_0
  openssl                   1.1.1d               he774522_0
  pefile                    2019.4.18                pypi_0    pypi
  pip                       19.2.2                   py37_0
  py-opencv                 3.4.2            py37hc319ecb_0
  pyinstaller               3.5.dev0+gb54a15d7          pypi_0    pypi
  pyqt                      5.9.2            py37h6538335_2
  pyqtgraph                 0.10.0           py37h28b3542_3
  python                    3.7.4                h5263a28_0
  pywin32-ctypes            0.2.0                    pypi_0    pypi
  qt                        5.9.7            vc14h73c81de_0
  qtpy                      1.9.0                      py_0
  scipy                     1.3.1            py37h29ff71c_0
  setuptools                41.0.1                   py37_0
  sip                       4.19.8           py37h6538335_0
  six                       1.12.0                   py37_0
  sqlite                    3.29.0               he774522_0
  tifffile                  0.15.1          py37h452e1ab_1001    conda-forge
  vc                        14.1                 h0510ff6_4
  vs2015_runtime            14.16.27012          hf0eaf9b_0
  wheel                     0.33.4                   py37_0
  wincertstore              0.2                      py37_0
  xz                        5.2.4                h2fa13f4_4
  zlib                      1.2.11               h62dcd97_3
  zstd                      1.3.7                h508b16e_0
  </code></pre>
  
  <p><strong>Update</strong> I can reproduce the behaviour, if I put only <code>import tifffile</code> into an empty python file and run pyinstaller on it. </p>