Address review comments.

Author: jmarrec

build.py

@@ -117,18 +117,18 @@ def Exit( self ):
 
 def FindLatestMSVC():
     import winreg
-    aReg = winreg.ConnectRegistry(None, winreg.HKEY_LOCAL_MACHINE)
+    handle = winreg.ConnectRegistry(None, winreg.HKEY_LOCAL_MACHINE)
     msvc = None
     for i in [17, 16, 15]:
         try:
-            aKey = winreg.OpenKey(aReg, rf'SOFTWARE\Microsoft\VisualStudio\{i}.0')
-            print(f"Found {i}")
+            winreg.OpenKey(handle, rf'SOFTWARE\Microsoft\VisualStudio\{i}.0')
             msvc = i
             break
         except FileNotFoundError:
             pass
     return msvc
 
+
 def RemoveDirectory( directory ):
   try_number = 0
   max_tries = 10
@@ -424,13 +424,8 @@ def ParseArguments():
                        help = 'Use system libclang instead of downloading one '
                        'from llvm.org. NOT RECOMMENDED OR SUPPORTED!' )
   if OnWindows():
-      latest_msvc = FindLatestMSVC()
-      if latest_msvc is None:
-          # TODO: raise?
-          # raise FileNotFoundError("Could not find a valid MSVC version")
-          latest_msvc = 16
       parser.add_argument( '--msvc', type = int, choices = [ 15, 16, 17 ],
-                          default=latest_msvc,
+                          default=None,
                           help= 'Choose the Microsoft Visual Studio version '
                                 '(default: %(default)s).' )
   parser.add_argument( '--ninja', action = 'store_true',
@@ -511,6 +506,11 @@ def ParseArguments():
     # We always want a debug build when running with coverage enabled
     args.enable_debug = True
 
+  if OnWindows() and args.msvc is None:
+    args.msvc = FindLatestMSVC()
+    if args.msvc is None:
+      raise FileNotFoundError("Could not find a valid MSVC version")
+
   if args.core_tests:
     os.environ[ 'YCM_TESTRUN' ] = '1'
   elif os.environ.get( 'YCM_TESTRUN' ):