core: parse line numbers for Vagrantfile syntax errors on Win [GH-6445]

CHANGELOG.md

@@ -69,6 +69,8 @@ BUG FIXES:
   - core: more robust check for admin privs on Windows [GH-5616]
   - core: properly detect when HTTP server doesn't support byte ranges and
       retry from scratch [GH-4479]
+  - core: line numbers show properly in Vagrantfile syntax errors
+      on Windows [GH-6445]
   - commands/box: the update command supports CA settings [GH-4473]
   - commands/box: removing all versions and providers of a box will properly
       clean all directories in `~/.vagrant.d/boxes` [GH-3570]

lib/vagrant/config/loader.rb

@@ -221,7 +221,12 @@ module Vagrant
 
             line = "(unknown)"
             if e.backtrace && e.backtrace[0]
-              line = e.backtrace[0].split(":")[1]
+              e.backtrace[0].split(":").each do |part|
+                if part =~ /\d+/
+                  line = part.to_i
+                  break
+                end
+              end
             end
 
             # Report the generic exception