add email simplate for failed charges

emails/charge_failed.spt

@@ -0,0 +1,30 @@
+{{ ngettext("Your payment failed!", "Your payments failed!", ntippees) }}
+
+[---] text/html
+{{ ngettext(
+    "We tried to charge your credit card {0} today, to fund your weekly payment to {1}, but it failed.",
+    "We tried to charge your credit card {0} today, to fund your weekly payments to {1}, but it failed.",
+    format_currency(exchange.amount, 'USD'),
+    top_tippee.username if ntippees == 1 else ngettext('{0} and {n} other', '{0} and {n} others', ntippees - 1, top_tippee.username)
+    ) }}
+
+{{ _("The error message we received from our payment processor is:") }}<pre>
+
+{{ exchange.note }}
+</pre>
+
+<a href="{{ participant.profile_url+'routes/credit-card.html' }}" style="{{ button_style }}">{{ _("Fix your credit card") }}</a>
+
+[---] text/plain
+{{ ngettext(
+    "We tried to charge your credit card {0} today, to fund your weekly payment to {1}, but it failed.",
+    "We tried to charge your credit card {0} today, to fund your weekly payments to {1}, but it failed.",
+    format_currency(exchange.amount, 'USD'),
+    top_tippee.username if ntippees == 1 else ngettext('{0} and {n} other', '{0} and {n} others', ntippees - 1, top_tippee.username)
+    ) }}
+
+{{ _("The error message we received from our payment processor is:") }}
+
+{{ exchange.note }}
+
+{{ _("Follow this link to fix your credit card:") }} {{ participant.profile_url+'routes/credit-card.html' }}

emails/verification.spt

@@ -6,7 +6,7 @@
      ('<b><a href="https://gratipay.com/{0}">{0}</a></b>'|safe).format(username)) }}
 <br>
 <br>
-<a href="{{ link }}" style="color: #fff; text-decoration:none; display:inline-block; padding: 0 15px; background: #396; font: normal 14px/40px Arial, sans-serif; white-space: nowrap; border-radius: 3px">{{ _("Yes, proceed!") }}</a>
+<a href="{{ link }}" style="{{ button_style }}">{{ _("Yes, proceed!") }}</a>
 
 [---] text/plain
 {{ _("We've received a request to connect {0} to the {1} account on Gratipay. Sound familiar?",

gratipay/models/participant.py

@@ -624,6 +624,11 @@ def remove_email(self, address):
 
     def send_email(self, spt_name, **context):
         context['username'] = self.username
+        context['button_style'] = (
+            "color: #fff; text-decoration:none; display:inline-block; "
+            "padding: 0 15px; background: #396; white-space: nowrap; "
+            "font: normal 14px/40px Arial, sans-serif; border-radius: 3px"
+        )
         context.setdefault('include_unsubscribe', True)
         email = context.setdefault('email', self.email_address)
         langs = i18n.parse_accept_lang(self.email_lang or 'en')