diff --git a/timesearch/commentaugment.py b/timesearch/commentaugment.py
index 73d622a..1514938 100644
--- a/timesearch/commentaugment.py
+++ b/timesearch/commentaugment.py
@@ -1,6 +1,7 @@
 import traceback
 
 from . import common
+from . import exceptions
 from . import tsdb
 
 
@@ -17,6 +18,9 @@ def commentaugment(
     Take the IDs of collected submissions, and gather comments from those threads.
     Please see the global DOCSTRING_COMMENTAUGMENT variable.
     '''
+    if not common.is_xor(subreddit, username):
+        raise exceptions.NotExclusive(['subreddit', 'username'])
+
     common.bot.login(common.r)
     if specific_submission is not None:
         if not specific_submission.startswith('t3_'):
@@ -24,9 +28,6 @@ def commentaugment(
         specific_submission_obj = common.r.submission(specific_submission[3:])
         subreddit = specific_submission_obj.subreddit.display_name
 
-    if (subreddit is None) == (username is None):
-        raise Exception('Enter subreddit or username but not both')
-
     if subreddit:
         if specific_submission is None:
             database = tsdb.TSDB.for_subreddit(subreddit, do_create=False)
diff --git a/timesearch/common.py b/timesearch/common.py
index b9120b1..3d6d09d 100644
--- a/timesearch/common.py
+++ b/timesearch/common.py
@@ -87,6 +87,12 @@ def int_none(x):
         return None
     return int(x)
 
+def is_xor(*args):
+    '''
+    Return True if and only if one arg is truthy.
+    '''
+    return [bool(a) for a in args].count(True) == 1
+
 def nofailrequest(function):
     '''
     Creates a function that will retry until it succeeds.
diff --git a/timesearch/exceptions.py b/timesearch/exceptions.py
index 9bd74b5..90b557c 100644
--- a/timesearch/exceptions.py
+++ b/timesearch/exceptions.py
@@ -27,3 +27,9 @@ class DatabaseOutOfDate(TimesearchException):
 
 class DatabaseNotFound(TimesearchException, FileNotFoundError):
     error_message = 'Database file not found: "{}"'
+
+class NotExclusive(TimesearchException):
+    '''
+    For when two or more mutually exclusive actions have been requested.
+    '''
+    error_message = 'One and only one of {} must be passed.'
diff --git a/timesearch/livestream.py b/timesearch/livestream.py
index c3a931d..8e8737d 100644
--- a/timesearch/livestream.py
+++ b/timesearch/livestream.py
@@ -3,6 +3,7 @@ import time
 import traceback
 
 from . import common
+from . import exceptions
 from . import tsdb
 
 
@@ -62,11 +63,6 @@ def livestream(
             print()
             return
 
-        except Exception:
-            traceback.print_exc()
-            print('Retrying in 5...')
-            time.sleep(5)
-
 hangman = lambda: livestream(
     username='gallowboob',
     do_submissions=True,
@@ -83,10 +79,11 @@ def _livestream_as_a_generator(
         params,
     ):
 
-    if bool(subreddit) == bool(username):
-        raise Exception('Require either username / subreddit parameter, but not both')
-    if bool(do_submissions) is bool(do_comments) is False:
-        raise Exception('Require do_submissions and/or do_comments parameter')
+    if not common.is_xor(subreddit, username):
+        raise exceptions.NotExclusive(['subreddit', 'username'])
+
+    if not any([do_submissions, do_comments]):
+        raise TypeError('Required do_submissions and/or do_comments parameter')
     common.bot.login(common.r)
 
     if subreddit:
@@ -129,8 +126,8 @@ def _livestream_helper(
 
     args and kwargs go into the collecting functions.
     '''
-    if bool(submission_function) is bool(comment_function) is False:
-        raise Exception('Require submissions and/or comments parameter')
+    if not any([submission_function, comment_function]):
+        raise TypeError('Required submissions and/or comments parameter')
     results = []
 
     if submission_function:
diff --git a/timesearch/offline_reading.py b/timesearch/offline_reading.py
index 16d6ae0..d1d91a2 100644
--- a/timesearch/offline_reading.py
+++ b/timesearch/offline_reading.py
@@ -2,6 +2,7 @@ import os
 import markdown
 
 from . import common
+from . import exceptions
 from . import tsdb
 
 
@@ -221,8 +222,8 @@ def html_from_database(subreddit=None, username=None, specific_submission=None):
     if markdown is None:
         raise ImportError('Page cannot be rendered without the markdown module')
 
-    if (subreddit is None) == (username is None):
-        raise Exception('Enter subreddit or username but not both')
+    if not common.is_xor(subreddit, username):
+        raise exceptions.NotExclusive(['subreddit', 'username'])
 
     if subreddit:
         database = tsdb.TSDB.for_subreddit(subreddit, do_create=False)
diff --git a/timesearch/redmash.py b/timesearch/redmash.py
index 01cd482..54d28e1 100644
--- a/timesearch/redmash.py
+++ b/timesearch/redmash.py
@@ -2,6 +2,7 @@ import datetime
 import os
 
 from . import common
+from . import exceptions
 from . import tsdb
 
 
@@ -52,8 +53,8 @@ def redmash(
         html=False,
         score_threshold=0,
     ):
-    if (subreddit is None) == (username is None):
-        raise Exception('Enter subreddit or username but not both')
+    if not common.is_xor(subreddit, username):
+        raise exceptions.NotExclusive(['subreddit', 'username'])
 
     if subreddit:
         database = tsdb.TSDB.for_subreddit(subreddit, do_create=False)
@@ -159,9 +160,6 @@ def redmash_worker(
     return mash_filepath
 
 def redmash_argparse(args):
-    if args.subreddit is args.username is None:
-        raise ValueError('-r subreddit OR -u username must be provided')
-
     return redmash(
         subreddit=args.subreddit,
         username=args.username,
diff --git a/timesearch/timesearch.py b/timesearch/timesearch.py
index ed7b0b7..bfbca27 100644
--- a/timesearch/timesearch.py
+++ b/timesearch/timesearch.py
@@ -2,6 +2,7 @@ import time
 import traceback
 
 from . import common
+from . import exceptions
 from . import tsdb
 
 
@@ -21,8 +22,8 @@ def timesearch(
     Collect submissions across time.
     Please see the global DOCSTRING variable.
     '''
-    if (subreddit is None) == (username is None):
-        raise Exception('Enter subreddit or username but not both')
+    if not common.is_xor(subreddit, username):
+        raise exceptions.NotExclusive(['subreddit', 'username'])
 
     common.bot.login(common.r)