Further reiterated the policy for pull requests

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,6 +6,8 @@
     be able to accept.
 
     Please indicate the relevant feature request or bug report below.
+    IF YOUR PULL REQUEST DOES NOT REFERENCE AN ACCEPTED BUG REPORT OR
+    FEATURE REQUEST, IT WILL BE MARKED AS INVALID AND CLOSED.
 -->
 ### Fixes:
 

CONTRIBUTING.md

@@ -91,11 +91,13 @@ appropriate labels will be applied for categorization.
 
 ## Submitting Pull Requests
 
-* Be sure to open an issue before starting work on a pull request, and discuss
-your idea with the NetBox maintainers before beginning work​. This will help
-prevent wasting time on something that might we might not be able to implement.
-When suggesting a new feature, also make sure it won't conflict with any work
-that's already in progress.
+* Be sure to open an issue **before** starting work on a pull request, and
+discuss your idea with the NetBox maintainers before beginning work. This will
+help prevent wasting time on something that might we might not be able to
+implement. When suggesting a new feature, also make sure it won't conflict with
+any work that's already in progress.
+
+* Any pull request which does _not_ relate to an accepted issue will be closed.
 
 * When submitting a pull request, please be sure to work off of the `develop`
 branch, rather than `master`. The `develop` branch is used for ongoing