2488453 - Import of custom theme in portal fails due to java.lang.RuntimeException: org.mozilla.javascript.JavaScriptException

You try to import a custom portal theme of the old structure (Legacy Mode) to your portal which is in the new theming structure(LESS Mode), and it fails. You will get error message: Log contains errors. Check the log file.
In the server defaullttraces you might see:

Failed to convert theme <Custom Theme> from old structure to new structure
[EXCEPTION]
java.lang.RuntimeException: org.mozilla.javascript.JavaScriptException: sap.theming.less.NonExistingEntityException:Loading Framework "Base" failed. No configuration found.
  in code "sap.theming.less.BaseFramework.bApplyMetaData"
  while processing entity "Base" (system.js\#54)
Caused by: org.mozilla.javascript.JavaScriptException: [object Object] (system.js\#54)

or

Script Engine Logger : sap.theming.less.NonExistingEntityException:Loading Framework "UI5" failed. No configuration found.
in code "sap.theming.less.UI5Framework.bApplyMetaData"
while processing entity "UI5"
at org.mozilla.javascript.ScriptRuntime.constructError(ScriptRuntime.java:3687)

Failed to convert theme from old structure to new structure
[EXCEPTION]
java.lang.RuntimeException: org.mozilla.javascript.JavaScriptException: sap.theming.less.NonExistingEntityException:Loading Framework "UI5" failed. No configuration found.
in code "sap.theming.less.UI5Framework.bApplyMetaData"
while processing entity "UI5"

• NetWeaver AS Java
• NetWeaver Enterprise Portal(7.40 SP14 and above or 750 SP06,  with UISAPUI5_JAVA SCA of 7.50 SP07 and above.)

theme import error, log contains errors, check the log file, LESS, Legacy, UI Theme Designer, Transport Themes, theme editor, old structure, new structure, Loading Framework "Base" failed, No configuration found, org.mozilla.javascript.JavaScriptException , KBA , EP-PIN-TOL-UTD , UI Theme Designer in Portal & new theme structure issues , Problem