Change response to packageVersionNotFound from badRequest in case of

parsing issues or missing artifacts at the repo. This normalizes the API somewhat.

analyzer/restapi-plugin/src/main/java/eu/fasten/analyzer/restapiplugin/api/PackageApi.java

@@ -82,7 +82,7 @@ ResponseEntity<String> getPackageVersion(@PathVariable("pkg") String packageName
             return Responses.ok(result);
         }
         catch (IllegalArgumentException e) {
-            return Responses.badRequest();
+            return Responses.packageVersionNotFound();
         }
      }
 
@@ -103,7 +103,7 @@ ResponseEntity<String> getPackageMetadata(@PathVariable("pkg") String packageNam
             return Responses.ok(result);
         }
         catch (IllegalArgumentException e) {
-            return Responses.badRequest();
+            return Responses.packageVersionNotFound();
         }
     }
 
@@ -126,7 +126,7 @@ ResponseEntity<String> getPackageCallgraph(@PathVariable("pkg") String packageNa
             return Responses.ok(result);
         }
         catch (IllegalArgumentException e) {
-            return Responses.badRequest();
+            return Responses.packageVersionNotFound();
         }
     }