printing: Update documentation and test

Now that printing isn't loaded automatically
it must be loaded explicitly.

Fixes: 4f7f090 An attempt to solve printing import error
Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.st>

Author: asbjornst

mapnik/printing/__init__.py

@@ -65,6 +65,7 @@ class PDFPrinter(object):
     Main class for creating PDF print outs. Basic usage is along the lines of
 
     import mapnik
+    import mapnik.printing
 
     page = mapnik.printing.PDFPrinter()
     m = mapnik.Map(100,100)

test/python_tests/pdf_printing_test.py

@@ -31,6 +31,8 @@ def make_pdf(m, output_pdf, esri_wkt):
 	page.add_geospatial_pdf_header(m, output_pdf, wkt=esri_wkt)
 
 if mapnik.has_pycairo():
+	import mapnik.printing
+
 	def test_pdf_printing():
 		source_xml = '../data/good_maps/marker-text-line.xml'.encode('utf-8')
 		m = make_map_from_xml(source_xml)