Error stating Entity map does not exist on target when the solution contains no relationships
<p>I start in the DEV environment</p>

<ul>
<li><p>I created a blank solution.</p></li>
<li><p>I added Business Unit entity to it</p></li>
<li><p>I did not add any subcomponent, left "Include entity metadata" checked</p></li>
<li><p>I then went to Components -> Entities -> Business Unit, expanded Fields, clicked Add Subcomponents</p></li>
<li><p>I picked one Rollup custom field, left "Include entity metadata" checked</p></li>
</ul>

<p>I exported the solution as Unmanaged</p>

<p>I opened the STAGING environment (same as DEV except for the customizations I'm trying to bring over from DEV)</p>

<p>I tried to import the solution. Import <strong><em>fails</em></strong>.</p>

<p>This is the error (copy-pasted from the log file, reformatted for readability):</p>

<blockquote>
  <p>Entity Mapping</p>
  
  <p>businessunit-opportunity</p>
  
  <p>Failure</p>
  
  <p>0x80048010</p>
  
  <p>EntityMap businessunit -> opportunity - Import: FAILURE. This entity map does not exist on the target system.</p>
</blockquote>

<p>What is the CRM trying (and failing) to do ? Everything related to Business Unit (custom and/or standard) already exists in the target environment, I literally only have this custom field to bring over (I can go and create it by hand of course, but I'd rather stick to solutions...)</p>