Bitbucket: when OAuth consumer authentication fails mention that the `This is a private consumer` needs to be enabled (#10678)

src/Composer/Util/Bitbucket.php

@@ -112,9 +112,10 @@ class Bitbucket
         } catch (TransportException $e) {
             if ($e->getCode() === 400) {
                 $this->io->writeError('<error>Invalid OAuth consumer provided.</error>');
-                $this->io->writeError('This can have two reasons:');
+                $this->io->writeError('This can have three reasons:');
                 $this->io->writeError('1. You are authenticating with a bitbucket username/password combination');
                 $this->io->writeError('2. You are using an OAuth consumer, but didn\'t configure a (dummy) callback url');
+                $this->io->writeError('3. You are using an OAuth consumer, but didn\'t configure it as private consumer');
 
                 return false;
             }

tests/Composer/Test/Util/BitbucketTest.php

@@ -197,9 +197,10 @@ class BitbucketTest extends TestCase
             ->method('writeError')
             ->withConsecutive(
                 array('<error>Invalid OAuth consumer provided.</error>'),
-                array('This can have two reasons:'),
+                array('This can have three reasons:'),
                 array('1. You are authenticating with a bitbucket username/password combination'),
-                array('2. You are using an OAuth consumer, but didn\'t configure a (dummy) callback url')
+                array('2. You are using an OAuth consumer, but didn\'t configure a (dummy) callback url'),
+                array('3. You are using an OAuth consumer, but didn\'t configure it as private consumer')
             );
 
         $this->httpDownloader->expects($this->once())