issues introduced with 51cf70bdf8445e1d46d81f2a9d7c9b4aab113c99

[looooo]

• some widgets get added twice

[looooo]

• widget not shown at all

[looooo]

• missing file:

  ======================================================================
  ERROR: test_export_plots (test_glider_exports.TestGlider)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
  File "/home/travis/build/booya-at/OpenGlider/tests/test_glider_exports.py", line 80, in test_export_plots
  all.export_dxf(dxfile)
  File "/home/travis/build/booya-at/OpenGlider/openglider/plots/drawing/layout.py", line 496, in export_dxf
  drawing = ezdxf.new(dxfversion=dxfversion)
  File "/home/travis/miniconda/envs/test-environment/lib/python3.6/site-packages/ezdxf/filemanagement.py", line 32, in new
  dwg = Drawing.new(dxfversion)
  File "/home/travis/miniconda/envs/test-environment/lib/python3.6/site-packages/ezdxf/drawing.py", line 353, in new
  stream = finder.getstream(dxfversion.upper())
  File "/home/travis/miniconda/envs/test-environment/lib/python3.6/site-packages/ezdxf/templates/__init__.py", line 35, in getstream
  return io.open(self.filepath(dxfversion), encoding='cp1252')
  FileNotFoundError: [Errno 2] No such file or directory: '/home/travis/miniconda/envs/test-environment/lib/python3.6/site-packages/ezdxf/templates/AC1015.dxf'

[looooo]

seems to be an issue with ezdxf.