Add an cancel reason to the error message for execution "In Silico PCR" workflow

Scenario

1. Load "In Silico PCR" workflow example
2. Select Read Sequence and set sequence to ../samples/fastq/eas.fastq
3. Select In Silico PCR and set primer to  data/primer3/rodrep_and_simple.txt
4. Run worklow, it finished with "Subtask {In silico PCR workflow task} is canceled" error message without error reason.
   The cause of the error is found if you enable detailed view, save log in temporary file and search for "cancel" word:

Primer sequence is too long: MML1 Mouse L1 repetitive sequence.. The pair is skipped
Primer sequence is too long: PLMYS1 Mouse mys-1 transposon.. The pair is skipped
Promoting task {Read document: 'rodrep_and_simple.txt'} to 'Finished'
reducing bus from key=read-sequence:sequence to=sequence
reducing bus from key=read-sequence:sequence to=sequence
Promoting task {Multiple In Silico PCR} to 'Prepared'
Promoting task {In silico PCR workflow task} to 'Prepared'
One of the given do not fits acceptable length. Task cancelled. 

Add "One of the given primers do not fits acceptable length. It is too long." in the error message.