Adds a user to a specified issue's watcher list.

        Arguments:
            |  issue (string)  		| A JIRA Issue that a watcher needs added to, can be an issue ID or Key		|
            |  JIRAUsername (string)  	| A JIRA Username to add as a watcher to an issue   					|

        Example:
            |  *Keyword*        	|  *Parameters* | 								|		|
            |  connect to jira  |  asimmons     | options= {'http://devjira01'}     | 		|
            |  ${issue}				|  create issue |  ${issue_field_dict}			|  True |
            |  add watcher to issue	|  ${issue}		|  aSample 						| 		|

def add_watcher_to_issue(self, issue, JIRAUsername):
        """
        Adds a user to a specified issue's watcher list.

        Arguments:
            |  issue (string)  		| A JIRA Issue that a watcher needs added to, can be an issue ID or Key		|
            |  JIRAUsername (string)  	| A JIRA Username to add as a watcher to an issue   					|

        Example:
            |  *Keyword*        	|  *Parameters* | 								|		|
            |  connect to jira  |  asimmons     | options= {'http://devjira01'}     | 		|
            |  ${issue}				|  create issue |  ${issue_field_dict}			|  True |
            |  add watcher to issue	|  ${issue}		|  aSample 						| 		|

        """
        self.jira.add_watcher(issue=issue, watcher=JIRAUsername)