title: Getting "django.core.exceptions.ImproperlyConfigured: GEOS is required and has not been detected." although GEOS is installed
body: <p>I'm running <em>Django 1.8</em> and <em>Python 3.4</em> on <em>Ubuntu 14.04 LTS</em>. Just recently, my Django app has been reporting that <strong>GEOS</strong> is not present. <strong>GEOS</strong> is installed and <strong>libgeos_c.so</strong> is where it's supposed to be (<em>/usr/lib/</em>). My code seems fine. It is the source of a docker image which still works. This seems to indicate an os/incompatibility issue. Any help would be much appreciated.</p>
  
  <p>The full traceback is</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydevd.py", line 2358, in &lt;module&gt;
      globals = debugger.run(setup['file'], None, None, is_module)
    File "&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydevd.py", line 1778, in run
      pydev_imports.execfile(file, globals, locals)  # execute the script
    File "&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
      exec(compile(contents+"\n", file, 'exec'), glob, loc) 
    File "&lt;path/to/my/pycharm/project&gt;/manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
      utility.execute()
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/core/management/__init__.py", line 312, in execute
      django.setup()
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/__init__.py", line 18, in setup
      apps.populate(settings.INSTALLED_APPS)
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/apps/registry.py", line 108, in populate
      app_config.import_models(all_models)
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/apps/config.py", line 198, in import_models
      self.models_module = import_module(models_module_name)
    File "/usr/lib/python3.4/importlib/__init__.py", line 109, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "&lt;frozen importlib._bootstrap&gt;", line 2231, in _gcd_import
    File "&lt;frozen importlib._bootstrap&gt;", line 2214, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 2203, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1200, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1129, in _exec
    File "&lt;frozen importlib._bootstrap&gt;", line 1448, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 321, in _call_with_frames_removed
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/auth/models.py", line 41, in &lt;module&gt;
      class Permission(models.Model):
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/models/base.py", line 139, in __new__
      new_class.add_to_class('_meta', Options(meta, **kwargs))
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/models/base.py", line 324, in add_to_class
      value.contribute_to_class(cls, name)
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/models/options.py", line 250, in contribute_to_class
      self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/__init__.py", line 36, in __getattr__
      return getattr(connections[DEFAULT_DB_ALIAS], item)
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/utils.py", line 240, in __getitem__
      backend = load_backend(db['ENGINE'])
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/db/utils.py", line 111, in load_backend
      return import_module('%s.base' % backend_name)
    File "/usr/lib/python3.4/importlib/__init__.py", line 109, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "&lt;frozen importlib._bootstrap&gt;", line 2231, in _gcd_import
    File "&lt;frozen importlib._bootstrap&gt;", line 2214, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 2203, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1200, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1129, in _exec
    File "&lt;frozen importlib._bootstrap&gt;", line 1448, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 321, in _call_with_frames_removed
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/db/backends/postgis/base.py", line 8, in &lt;module&gt;
      from .features import DatabaseFeatures
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/db/backends/postgis/features.py", line 1, in &lt;module&gt;
      from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/db/backends/base/features.py", line 3, in &lt;module&gt;
      from django.contrib.gis.db.models import aggregates
    File "&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/db/models/__init__.py", line 12, in &lt;module&gt;
      "See also https://docs.djangoproject.com/en/%s/ref/contrib/gis/install/geolibs/" % get_docs_version())
  django.core.exceptions.ImproperlyConfigured: GEOS is required and has not been detected. Are you sure it is installed? See also https://docs.djangoproject.com/en/1.8/ref/contrib/gis/install/geolibs/
  </code></pre>
  
  <p>I've tried reinstalling <strong>libgdal-dev</strong>. All relevant packages (GDAL, GEOS etc) are up to date.</p>
  
  <p>I've tried working my way back through the Python code. it fails in <strong>djanjo/contrib/gis/geos/__init__.py</strong> on the following. As HAS_GEOS is set to false it reports that GEOS is not present. </p>
  
  <pre><code>try:
      from .libgeos import geos_version, geos_version_info  # NOQA: flake8 detects only the last __all__
      HAS_GEOS = True
      __all__ += ['geos_version', 'geos_version_info']
  except ImportError:
      HAS_GEOS = False
  </code></pre>
  
  <p>I suspect that a recent OS upgrade/patch has broken GEOS or GDAL. The root cause seems to be something to do with <strong>ctypes</strong>, but I can't see what it could be.</p>
  
  <p>The following might be useful.</p>
  
  <pre><code>&gt;&gt;&gt; from _ctypes import Union, Structure, Array
  Traceback (most recent call last):
    File "&lt;input&gt;", line 1, in &lt;module&gt;
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
  ImportError: /usr/lib/python3.4/lib-dynload/_ctypes.cpython-34m-x86_64-linux-gnu.so: undefined symbol: _PyTraceback_Add
  
  
  &gt;&gt;&gt; from django.contrib.gis import gdal
  Traceback (most recent call last):
    File "&lt;input&gt;", line 1, in &lt;module&gt;
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
    File "/&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/gdal/__init__.py", line 47, in &lt;module&gt;
      from django.contrib.gis.gdal.driver import Driver  # NOQA
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
    File "/&lt;path/to/my/virtualenv&gt;/lib/python3.4/site-packages/django/contrib/gis/gdal/driver.py", line 1, in &lt;module&gt;
      from ctypes import c_void_p
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
    File "/usr/lib/python3.4/ctypes/__init__.py", line 7, in &lt;module&gt;
      from _ctypes import Union, Structure, Array
    File "/&lt;path/to/my/homedir&gt;/pycharm-4.5.1/helpers/pydev/pydev_import_hook.py", line 21, in do_import
      module = self._system_import(name, *args, **kwargs)
  ImportError: /usr/lib/python3.4/lib-dynload/_ctypes.cpython-34m-x86_64-linux-gnu.so: undefined symbol: _PyTraceback_Add
  </code></pre>