refactor no cards found exit case to be more pythonic (#123)

replace counting loop with len()

mtgs_scraper.py

@@ -42,10 +42,7 @@ def parse_mtgs(mtgs, manual_cards=[], card_corrections=[], delete_cards=[], rela
             cards.remove(card)
 
     # if we didn't find any cards, let's bail out to prevent overwriting good data
-    count = 0
-    for card in cards:
-        count = count + 1
-    if count < 1:
+    if len(cards) < 1:
         sys.exit("No cards found, exiting to prevent file overwrite")
 
     cards2 = []
@@ -270,4 +267,4 @@ def list_mtgs_gallery(url=''):
     cardstree = tree.xpath('//*[contains(@class, "log-card")]')
     for child in cardstree:
         cards.append(child.text)
-    return cards
+    return cards