pkg/pub_semver: remove analyzer warnings

lib/src/version.dart

Index: lib/src/version.dart
diff --git a/lib/src/version.dart b/lib/src/version.dart
index 2821e27e392deae8ff1b4e2d0984308910450fe4..2bf535fcc94f2687c5809e9b1d721f5cfea58b68 100644
--- a/lib/src/version.dart
+++ b/lib/src/version.dart
@@ -122,7 +122,7 @@ class Version implements Comparable<Version>, VersionConstraint {
       String build = match[8];
 
       return new Version._(major, minor, patch, preRelease, build, text);
-    } on FormatException catch (ex) {
+    } on FormatException {
       throw new FormatException('Could not parse "$text".');
     }
   }
@@ -149,7 +149,7 @@ class Version implements Comparable<Version>, VersionConstraint {
     return text.split('.').map((part) {
       try {
         return int.parse(part);
-      } on FormatException catch (ex) {
+      } on FormatException {
         // Not a number.
         return part;
       }