Only warn for plugin conflicts when :pedantic? is :warn or :abort.

leiningen-core/project.clj

@@ -3,6 +3,7 @@
   :license {:name "Eclipse Public License"
             :url "http://www.eclipse.org/legal/epl-v10.html"}
   :description "Library for core functionality of Leiningen."
+  ;; If you update these, update resources/leiningen/bootclasspath-deps.clj too
   :dependencies [[org.clojure/clojure "1.8.0"]
                  [bultitude "0.2.8" :exclusions [org.tcrawley/dynapath]]
                  [org.flatland/classlojure "0.7.1"]

leiningen-core/src/leiningen/core/classpath.clj

@@ -411,7 +411,7 @@
   "When using the bootclasspath (for boot speed), resources already on the
   bootclasspath cannot be overridden by plugins, so notify the user about it."
   [project dependencies]
-  (when (:pedantic? project)
+  (when (#{:warn :abort} (:pedantic? project))
     (let [warned (atom false)]
       (doseq [[artifact version] dependencies
               :when (and (bootclasspath-deps artifact)

project.clj

@@ -6,6 +6,7 @@
   :url "https://github.com/technomancy/leiningen"
   :license {:name "Eclipse Public License"
             :url "http://www.eclipse.org/legal/epl-v10.html"}
+  ;; If you update these, update resources/leiningen/bootclasspath-deps.clj too
   :dependencies [[leiningen-core "2.8.0-SNAPSHOT"]
                  ;; needed for pom
                  [org.clojure/data.xml "0.0.8"]

sample.project.clj

@@ -77,9 +77,9 @@
   ;; What to do in the case of version conflicts. Defaults to :ranges, which
   ;; warns when version ranges are present anywhere in the dependency tree,
   ;; but can be set to true to warn for both ranges and overrides, or :abort
-  ;; to exit in the case of ranges or overrides. Setting this will also warn
-  ;; you when plugins or their dependencies conflict with libraries used by
-  ;; Leiningen itself.
+  ;; to exit in the case of ranges or overrides. Setting this to :warn or
+  ; :abort will also warn you when plugins or their dependencies
+  ; conflict with libraries used by Leiningen itself.
   :pedantic? :abort
   ;; Global exclusions are applied across the board, as an alternative
   ;; to duplication for multiple dependencies with the same excluded libraries.