Fix traceback when +python3 is not availble

autoload/vimspector.vim

@@ -13,6 +13,9 @@
 " See the License for the specific language governing permissions and
 " limitations under the License.
 
+if !has( 'python3' )
+  finish
+endif
 
 " Boilerplate {{{
 let s:save_cpo = &cpoptions

docs/configuration.md

@@ -271,7 +271,7 @@ JSON value `true`, and the suffix is stripped fom the key, resulting in the
 following:
 
 ```json
-  "stopOnEntry#json": true
+  "stopOnEntry": true
 ```
 
 Which is what we need.

plugin/vimspector.vim

@@ -13,6 +13,13 @@
 " See the License for the specific language governing permissions and
 " limitations under the License.
 
+if !has( 'python3' )
+  echohl WarningMsg
+  echom 'Vimspector unavailable: Requires Vim compiled with +python3'
+  echohl None
+  finish
+endif
+
 " Boilerplate {{{
 let s:save_cpo = &cpoptions
 set cpoptions&vim