Support size 15 and 16 quoted usernames

As usernames containing special characters must be quoted, they
may have two extra characters that are not counted against the
size limit of 16 characters. This patch adds a regex to handle
this case.

lib/puppet/type/mysql_user.rb

@@ -15,7 +15,7 @@
       raise(ArgumentError, "Database user #{value} must be quotted as it contains special characters") if value =~ /^[^'`"].*[^0-9a-zA-Z$_].*[^'`"]@[\w%\.:]+/
       raise(ArgumentError, "Invalid database user #{value}") unless value =~ /^(?:['`"][^'`"]*['`"]|[0-9a-zA-Z$_]*)@[\w%\.:]+/
       username = value.split('@')[0]
-      if username.size > 16
+      if not ((username =~ /['"`]*['"`]$/ and username.size <= 18) or username.size <= 16)
         raise ArgumentError, 'MySQL usernames are limited to a maximum of 16 characters'
       end
     end

spec/unit/puppet/type/mysql_user_spec.rb

@@ -49,6 +49,24 @@
     end
   end
 
+  context 'using a quoted 16 char username' do
+    before :each do
+      @user = Puppet::Type.type(:mysql_user).new(:name => '"debian-sys-maint"@localhost', :password_hash => 'pass')
+    end
+
+    it 'should accept a user name' do
+      expect(@user[:name]).to eq('"debian-sys-maint"@localhost')
+    end
+  end
+
+  context 'using a quoted username that is too long ' do
+    it 'should fail with a size error' do
+      expect {
+        Puppet::Type.type(:mysql_user).new(:name => '"debian-sys-maint2"@localhost', :password_hash => 'pass')
+      }.to raise_error /MySQL usernames are limited to a maximum of 16 characters/
+    end
+  end
+
   context 'using `speci!al#`@localhost' do
     before :each do
       @user = Puppet::Type.type(:mysql_user).new(:name => '`speci!al#`@localhost', :password_hash => 'pass')