Implementing reviewer's comments.

Author: staudtMarius

src/main/java/edu/ie3/datamodel/io/source/RawGridSource.java

@@ -158,7 +158,10 @@ public RawGridElements getGridData(
 
     if (!exceptions.isEmpty()) {
       throw new RawGridException(
-          "Some exception(s) occurred while initializing raw grid.", exceptions);
+          "Exception(s) occurred in "
+              + exceptions.size()
+              + " input files while initializing raw grid.",
+          exceptions);
     } else {
       /* build and return the grid if it is not empty */
       // getOrThrow should not throw an exception in this context, because all exception are

src/main/java/edu/ie3/datamodel/io/source/SystemParticipantSource.java

@@ -225,7 +225,10 @@ public SystemParticipants getSystemParticipants(
 
     if (!exceptions.isEmpty()) {
       throw new SystemParticipantsException(
-          "Some exception(s) occurred while initializing system participants.", exceptions);
+          "Exception(s) occurred in "
+              + exceptions.size()
+              + " input files while initializing system participants.",
+          exceptions);
     } else {
       // if everything is fine, return a system participants container
       // getOrThrow should not throw an exception in this context, because all exception are

src/test/groovy/edu/ie3/datamodel/io/source/csv/CsvSystemParticipantSourceTest.groovy

@@ -76,7 +76,7 @@ class CsvSystemParticipantSourceTest extends Specification implements CsvTestDat
 
     Exception ex = systemParticipants.exception.get()
     ex.class == SystemParticipantsException
-    ex.message == "Some exception(s) occurred while initializing system participants.\n" +
+    ex.message == "Exception(s) occurred in 10 input files while initializing system participants.\n" +
     "        edu.ie3.datamodel.exceptions.SourceException: 1 exception(s) occurred within \"FixedFeedInInput\" data: \n" +
     "               edu.ie3.datamodel.exceptions.FactoryException: edu.ie3.datamodel.exceptions.SourceException: Entity with uuid 4ca90220-74c2-4369-9afa-a18bf068840d was not provided. Caused by: edu.ie3.datamodel.exceptions.SourceException: Entity with uuid 4ca90220-74c2-4369-9afa-a18bf068840d was not provided.\n" +
     "        edu.ie3.datamodel.exceptions.SourceException: 1 exception(s) occurred within \"PvInput\" data: \n" +