Use pytest_(un)configure to setup cache_directory

conftest.py

@@ -1 +1,34 @@
+import tempfile
+import shutil
+
+import jedi
+
+
 collect_ignore = ["setup.py"]
+
+
+# The following hooks (pytest_configure, pytest_unconfigure) are used
+# to modify `jedi.settings.cache_directory` because `clean_jedi_cache`
+# has no effect during doctests.  Without these hooks, doctests uses
+# user's cache (e.g., ~/.cache/jedi/).  We should remove this
+# workaround once the problem is fixed in py.test.
+#
+# See:
+# - https://github.com/davidhalter/jedi/pull/168
+# - https://bitbucket.org/hpk42/pytest/issue/275/
+
+jedi_cache_directory_orig = None
+jedi_cache_directory_temp = None
+
+
+def pytest_configure(config):
+    global jedi_cache_directory_orig, jedi_cache_directory_temp
+    jedi_cache_directory_orig = jedi.settings.cache_directory
+    jedi_cache_directory_temp = tempfile.mkdtemp(prefix='jedi-test-')
+    jedi.settings.cache_directory = jedi_cache_directory_temp
+
+
+def pytest_unconfigure(config):
+    global jedi_cache_directory_orig, jedi_cache_directory_temp
+    jedi.settings.cache_directory = jedi_cache_directory_orig
+    shutil.rmtree(jedi_cache_directory_temp)