Do not barf more than once when python is not found. Patch by blueyed.

autoload/UltiSnips.vim

@@ -8,14 +8,30 @@ endif
 let did_UltiSnips_autoload=1
 
 " Define dummy version of function called by autocommand setup in
-" ftdetect/UltiSnips.vim. If the function isn't defined (probably due to
-" using a copy of vim without python support) it will cause an error anytime a
-" new file is opened.
+" ftdetect/UltiSnips.vim and plugin/UltiSnips.vim.
+" If the function isn't defined (probably due to using a copy of vim
+" without python support) it would cause an error.
 function! UltiSnips#FileTypeChanged()
 endfunction
+function! UltiSnips#CursorMoved()
+endfunction
+function! UltiSnips#CursorMoved()
+endfunction
+function! UltiSnips#LeavingBuffer()
+endfunction
+function! UltiSnips#LeavingInsertMode()
+endfunction
 
 call UltiSnips#bootstrap#Bootstrap()
 if !exists("g:_uspy")
+   " Delete the autocommands defined in plugin/UltiSnips.vim and
+   " ftdetect/UltiSnips.vim.
+   augroup UltiSnips
+       au!
+   augroup END
+   augroup UltiSnipsFileType
+       au!
+   augroup END
    finish
 end
 

autoload/UltiSnips/bootstrap.vim

@@ -14,7 +14,7 @@ function! UltiSnips#bootstrap#Bootstrap()
                    echo  "UltiSnips requires py >= 2.6 or any py3"
                endif
                unlet g:_uspy
-               finish
+               return
            endif
            let g:_uspy=":py "
        endif

autoload/UltiSnips/map_keys.vim

@@ -1,6 +1,11 @@
 call UltiSnips#bootstrap#Bootstrap()
 
 function! UltiSnips#map_keys#MapKeys()
+    if !exists('g:_uspy')
+        " Do not map keys if bootstrapping failed (e.g. no Python).
+        return
+    endif
+
     " Map the keys correctly
     if g:UltiSnipsExpandTrigger == g:UltiSnipsJumpForwardTrigger
 

ftdetect/UltiSnips.vim

@@ -1,5 +1,8 @@
 " This has to be called before ftplugins are loaded. Therefore
 " it is here in ftdetect though it maybe shouldn't
 if has("autocmd")
-   autocmd FileType * call UltiSnips#FileTypeChanged()
+   augroup UltiSnipsFileType
+      au!
+      autocmd FileType * call UltiSnips#FileTypeChanged()
+   augroup END
 endif

plugin/UltiSnips.vim

@@ -57,10 +57,13 @@ function! UltiSnips_Anon(...)
     return call(function('UltiSnips#Anon'), a:000)
 endfunction
 
-au CursorMovedI * call UltiSnips#CursorMoved()
-au CursorMoved * call UltiSnips#CursorMoved()
-au BufLeave * call UltiSnips#LeavingBuffer()
-au InsertLeave * call UltiSnips#LeavingInsertMode()
+augroup UltiSnips
+    au!
+    au CursorMovedI * call UltiSnips#CursorMoved()
+    au CursorMoved * call UltiSnips#CursorMoved()
+    au BufLeave * call UltiSnips#LeavingBuffer()
+    au InsertLeave * call UltiSnips#LeavingInsertMode()
+augroup END
 
 call UltiSnips#map_keys#MapKeys()