Added Å to unit definition, added tests to check angstrom, µ problems

pint/default_en.txt

@@ -138,7 +138,7 @@ byte = 8 * bit = Bo = octet
 baud = bit / second = Bd = bps
 
 # Length
-angstrom = 1e-10 * meter = ångström = Å
+angstrom = 1e-10 * meter = Å = ångström = Å
 inch = 2.54 * centimeter = in = international_inch = inches = international_inches 
 foot = 12 * inch = ft = international_foot = feet = international_feet
 mile = 5280 * foot = mi = international_mile

pint/testsuite/test_issues.py

@@ -9,6 +9,7 @@
 from pint.util import ParserHelper
 
 from pint.compat import np, unittest, long_type
+from pint.errors import UndefinedUnitError
 from pint.testsuite import QuantityTestCase, helpers
 
 
@@ -269,6 +270,27 @@ def test_issue170b(self):
         self.assertEqual(iq, long(10))
         self.assertIsInstance(iq, long)
 
+    def test_angstrom_creation(self):
+        ureg = UnitRegistry()
+        try:
+            ureg.Quantity(2, 'Å')
+        except SyntaxError:
+            self.fail('Quantity with Å could not be created.')
+
+    def test_alternative_angstrom_definition(self):
+        ureg = UnitRegistry()
+        try:
+            ureg.Quantity(2, '\u212B')
+        except UndefinedUnitError:
+            self.fail('Quantity with Å could not be created.')
+
+    def test_micro_creation(self):
+        ureg = UnitRegistry()
+        try:
+            ureg.Quantity(2, 'µm')
+        except SyntaxError:
+            self.fail('Quantity with µ prefix could not be created.')
+
 
 @helpers.requires_numpy()
 class TestIssuesNP(QuantityTestCase):