How to catch all exception in database after save() in django?

I want to return these error messages to the html form and show where are wrong with this form.Is there a solution?Or maybe I should use raw SQL queries?Thanks for any advice.

For example:

models.py:

class GeneticCharacter(models.Model):
    StrainNo=models.CharField(max_length=10,primary_key=True)
    StrainName=models.CharField(max_length=10)
    SourceNo=models.IntegerField()
    ESBL=models.CharField(max_length=9,blank=True)
    AEM=models.CharField(max_length=12,blank=True)
    PMQR=models.CharField(max_length=15,blank=True)
    ISeq=models.CharField(max_length=12,blank=True)
    Replicon=models.CharField(max_length=10,blank=True)
    MLST_type=models.CharField(max_length=10,blank=True)
    PLG_type=models.CharField(max_length=2,blank=True)
    IsPat=models.BooleanField()

views.py

...
obj=GeneticCharacter()
obj.ESBL="a"*20
obj.AEM="a"*20
obj.save()
...

How can I catch all the exceptions?