Remove Python version check

Starting the Python interpreter to check its version is slow.

python/ycm/paths.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2015 YouCompleteMe contributors.
+# Copyright (C) 2015-2017 YouCompleteMe contributors.
 #
 # This file is part of YouCompleteMe.
 #
@@ -51,19 +51,20 @@ def Memoize( obj ):
 
 @Memoize
 def PathToPythonInterpreter():
+  # Not calling the Python interpreter to check its version as it significantly
+  # impacts startup time.
   from ycmd import utils
 
   python_interpreter = vim.eval( 'g:ycm_server_python_interpreter' )
-
   if python_interpreter:
-    if IsPythonVersionCorrect( python_interpreter ):
+    if _EndsWithPython( python_interpreter ):
       return python_interpreter
 
     raise RuntimeError( "Path in 'g:ycm_server_python_interpreter' option "
                         "does not point to a valid Python 2.6+ or 3.3+." )
 
   python_interpreter = _PathToPythonUsedDuringBuild()
-  if IsPythonVersionCorrect( python_interpreter ):
+  if _EndsWithPython( python_interpreter ):
     return python_interpreter
 
   # On UNIX platforms, we use sys.executable as the Python interpreter path.
@@ -72,8 +73,7 @@ def PathToPythonInterpreter():
   # interpreter path.
   python_interpreter = ( WIN_PYTHON_PATH if utils.OnWindows() else
                          sys.executable )
-
+  if _EndsWithPython( python_interpreter ):
-  if IsPythonVersionCorrect( python_interpreter ):
     return python_interpreter
 
   # As a last resort, we search python in the PATH. We prefer Python 2 over 3
@@ -84,8 +84,7 @@ def PathToPythonInterpreter():
   python_interpreter = utils.PathToFirstExistingExecutable( [ 'python2',
                                                               'python',
                                                               'python3' ] )
-
+  if python_interpreter:
-  if IsPythonVersionCorrect( python_interpreter ):
     return python_interpreter
 
   raise RuntimeError( "Cannot find Python 2.6+ or 3.3+. You can set its path "
@@ -104,34 +103,10 @@ def _PathToPythonUsedDuringBuild():
     return None
 
 
-def EndsWithPython( path ):
+def _EndsWithPython( path ):
   """Check if given path ends with a python 2.6+ or 3.3+ name."""
   return path and PYTHON_BINARY_REGEX.search( path ) is not None
 
 
-def IsPythonVersionCorrect( path ):
-  """Check if given path is the Python interpreter version 2.6+ or 3.3+."""
-  from ycmd import utils
-
-  if not EndsWithPython( path ):
-    return False
-
-  command = [ path,
-              # Disable site customize. Faster, and less likely to encounter
-              # issues with disconnected mounts (nfs, fuse, etc.)
-              '-S',
-              '-c',
-              "import sys;"
-              "major, minor = sys.version_info[ :2 ];"
-              "good_python = ( major == 2 and minor >= 6 ) "
-              "or ( major == 3 and minor >= 3 ) or major > 3;"
-              # If this looks weird, remember that:
-              #   int( True ) == 1
-              #   int( False ) == 0
-              "sys.exit( not good_python )" ]
-
-  return utils.SafePopen( command ).wait() == 0
-
-
 def PathToServerScript():
   return os.path.join( DIR_OF_YCMD, 'ycmd' )

python/ycm/tests/paths_test.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2016 YouCompleteMe contributors
+# Copyright (C) 2016-2017 YouCompleteMe contributors
 #
 # This file is part of YouCompleteMe.
 #
@@ -26,15 +26,15 @@ from ycm.tests.test_utils import MockVimModule
 MockVimModule()
 
 from nose.tools import ok_
-from ycm.paths import EndsWithPython
+from ycm.paths import _EndsWithPython
 
 
 def EndsWithPython_Good( path ):
-  ok_( EndsWithPython( path ) )
+  ok_( _EndsWithPython( path ) )
 
 
 def EndsWithPython_Bad( path ):
-  ok_( not EndsWithPython( path ) )
+  ok_( not _EndsWithPython( path ) )
 
 
 def EndsWithPython_Python2Paths_test():
@@ -50,7 +50,6 @@ def EndsWithPython_Python2Paths_test():
     yield EndsWithPython_Good, path
 
 
-
 def EndsWithPython_Python3Paths_test():
   python_paths = [
     'python3',