Make loading of qrencode and cairosvg optional

In particular, cairosvg is only used for the PNG format twitter cards,
so most functionality exists without it.

Make sure we import those modules conditionally only when needed and
handle the import exception. Also add an explicit attempt to load them
during system startup and write to the log if it fails, so it doesn't do
so silently.

1 files changed, 11 insertions, 6 deletions

diff --git a/postgresqleu/util/misc/baseinvoice.py b/postgresqleu/util/misc/baseinvoice.py
index 8d79492e..834f37bc 100755
--- a/postgresqleu/util/misc/baseinvoice.py
+++ b/postgresqleu/util/misc/baseinvoice.py
@@ -13,7 +13,6 @@ from reportlab.platypus.tables import Table, TableStyle
 from reportlab.platypus.flowables import Image
 from reportlab.pdfbase.pdfmetrics import registerFont, getFont
 from reportlab.pdfbase.ttfonts import TTFont
-import qrencode
 from io import BytesIO
 
 from django.conf import settings
@@ -324,11 +323,17 @@ class BaseInvoice(PDFBase):
             p.wrapOn(self.canvas, cm(12), cm(2))
             p.drawOn(self.canvas, cm(2), cm(3.5))
 
-            (ver, size, qrimage) = qrencode.encode(self.paymentlink)
-            qrimage = qrimage.resize((size * 4, size * 4))
-            self.canvas.drawImage(ImageReader(qrimage),
-                                  cm(2), cm(1.8),
-                                  cm(1.5), cm(1.5))
+            try:
+                import qrencode
+                (ver, size, qrimage) = qrencode.encode(self.paymentlink)
+                qrimage = qrimage.resize((size * 4, size * 4))
+                self.canvas.drawImage(ImageReader(qrimage),
+                                      cm(2), cm(1.8),
+                                      cm(1.5), cm(1.5))
+            except ImportError:
+                # If we don't have the qrcode module, we just don't bother drawing the
+                # QR code for the link
+                pass
 
             if self.reverse_vat:
                 t = self.canvas.beginText()