Only importing ycm_core in ycmd

I'm not sure, but it seems that loading both ycm_client_support and ycm_core
into the same process is causing random ycmd crashes.

python/ycm/completers/completer.py

@@ -18,8 +18,13 @@
 # along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.
 
 import abc
-import ycm_client_support
-from ycm.utils import ToUtf8IfNeeded, ForceSemanticCompletion
+from ycm.utils import ToUtf8IfNeeded, ForceSemanticCompletion, RunningInsideVim
+
+if RunningInsideVim():
+  from ycm_client_support import FilterAndSortCandidates
+else:
+  from ycm_core import FilterAndSortCandidates
+
 from ycm.completers.completer_utils import TriggersForFiletype
 
 NO_USER_COMMANDS = 'This completer does not define any commands.'
@@ -206,10 +211,9 @@ class Completer( object ):
     elif 'insertion_text' in candidates[ 0 ]:
       sort_property = 'insertion_text'
 
-    matches = ycm_client_support.FilterAndSortCandidates(
-      candidates,
-      sort_property,
-      ToUtf8IfNeeded( query ) )
+    matches = FilterAndSortCandidates( candidates,
+                                       sort_property,
+                                       ToUtf8IfNeeded( query ) )
 
     return matches
 

python/ycm/utils.py

@@ -62,6 +62,14 @@ def MakeFolderAccessibleToAll( path_to_folder ):
   os.chmod( path_to_folder, flags )
 
 
+def RunningInsideVim():
+  try:
+    import vim  # NOQA
+    return True
+  except ImportError:
+    return False
+
+
 def GetUnusedLocalhostPort():
   sock = socket.socket()
   # This tells the OS to give us any free port in the range [1024 - 65535]