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J'ai aussi un problème : voici le message d'erreur que je reçois lorsque j'installe l'extension Openlayers Plugin, je pense que c'est bien de celle-ci il est question. Voici le message reçu :
Impossible de charger l'extension openlayers_plugin provoque une erreur lors de l'appel de sa méthode initGui()

TypeError: setHostName(self, QString): argument 1 has unexpected type 'QPyNullVariant'
Traceback (most recent call last):
  File "/Applications/QGIS.app/Contents/MacOS/../Resources/python/qgis/utils.py", line 342, in startPlugin
    plugins[packageName].initGui()
  File "/Users/Anne-Marie/.qgis2/python/plugins/openlayers_plugin/openlayers_plugin.py", line 156, in initGui
    self.setGDALProxy()
  File "/Users/Anne-Marie/.qgis2/python/plugins/openlayers_plugin/openlayers_plugin.py", line 316, in setGDALProxy
    proxy = getProxy()
  File "/Users/Anne-Marie/.qgis2/python/plugins/openlayers_plugin/tools_network.py", line 40, in getProxy
    proxy.setHostName(settings.value("/proxyHost"))
TypeError: setHostName(self, QString): argument 1 has unexpected type 'QPyNullVariant'


Version de Python : 2.7.10 (default, Oct 23 2015, 19:19:21) [GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)]
Version de QGIS : 2.18.15 Las Palmas, exported

Chemin Python :
/Applications/QGIS.app/Contents/MacOS/../Resources/python/plugins/processing
/Applications/QGIS.app/Contents/MacOS/../Resources/python
/Users/Anne-Marie/.qgis2/python
/Users/Anne-Marie/.qgis2/python/plugins
/Applications/QGIS.app/Contents/MacOS/../Resources/python/plugins
/Library/Frameworks/SQLite3.framework/Versions/C/Python/2.7
/Library/Frameworks/GEOS.framework/Versions/3/Python/2.7/site-packages
/Library/Python/2.7/site-packages/scipy-override
/Library/Python/2.7/site-packages/numpy-override
/Library/Python/2.7/site-packages/matplotlib-override
/Library/Frameworks/GDAL.framework/Versions/2.1/Python/2.7/site-packages
/Library/Frameworks/cairo.framework/Versions/1/Python/2.7
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages
/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload
/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/PyObjC
/Library/Python/2.7/site-packages
/Library/Python/2.7/site-packages/PIL
/Users/Anne-Marie/.qgis2//python

Je comprend qu'il s'agit d'un problème de bibliothèque Python, quequn peut-il m'éclairer davantage ? Installation : QGIS 2-18-15 ( Kingchoas) sur Mac Os El Capitan