docs(codeforces.error): Add docstrings to codeforces/error.py

Author: Mukundan314

codeforces/error.py

@@ -1,6 +1,11 @@
+"""All exceptions used in codeforces."""
+
 __all__ = ['CodeforcesAPIError']
 
+
 class CodeforcesAPIError(Exception):
+    """Raised by api.call if method returns a error or is not found."""
+
     def __init__(self, comment, method, args):
         self.comment = comment
         self.method = method