Use whereis_exe to check for binaries

plyer/platforms/linux/battery.py

@@ -1,5 +1,6 @@
 from subprocess import Popen, PIPE
 from plyer.facades import Battery
+from plyer.utils import whereis_exe
 
 
 class LinuxBattery(Battery):
@@ -31,4 +32,8 @@ def _get_status(self):
 
 
 def instance():
-    return LinuxBattery()
+    import sys
+    if whereis_exe('upower'):
+        return LinuxBattery()
+    sys.stderr.write("upower not found.")
+    return Battery()

plyer/platforms/linux/email.py

@@ -1,6 +1,7 @@
 import subprocess
 from urllib import quote
 from plyer.facades import Email
+from plyer.utils import whereis_exe
 
 
 class LinuxEmail(Email):
@@ -26,4 +27,8 @@ def _send(self, **kwargs):
 
 
 def instance():
-    return LinuxEmail()
+    import sys
+    if whereis_exe('xdg-open'):
+        return LinuxEmail()
+    sys.stderr.write("xdg-open not found.")
+    return Email()

plyer/platforms/linux/uniqueid.py

@@ -1,5 +1,6 @@
 from subprocess import Popen, PIPE
 from plyer.facades import UniqueID
+from plyer.utils import whereis_exe
 
 
 class LinuxUniqueID(UniqueID):
@@ -17,4 +18,8 @@ def _get_uid(self):
 
 
 def instance():
-    return LinuxUniqueID()
+    import sys
+    if whereis_exe('lshw'):
+        return LinuxUniqueID()
+    sys.stderr.write("lshw not found.")
+    return UniqueID()

plyer/platforms/macosx/battery.py

@@ -1,5 +1,6 @@
 from subprocess import Popen, PIPE
 from plyer.facades import Battery
+from plyer.utils import whereis_exe
 
 
 class OSXBattery(Battery):
@@ -32,4 +33,8 @@ def _get_status(self):
 
 
 def instance():
-    return OSXBattery()
+    import sys
+    if whereis_exe('ioreg'):
+        return OSXBattery()
+    sys.stderr.write("ioreg not found.")
+    return Battery()

plyer/platforms/macosx/email.py

@@ -1,6 +1,7 @@
 import subprocess
 from urllib import quote
 from plyer.facades import Email
+from plyer.utils import whereis_exe
 
 
 class MacOSXEmail(Email):
@@ -26,4 +27,8 @@ def _send(self, **kwargs):
 
 
 def instance():
-    return MacOSXEmail()
+    import sys
+    if whereis_exe('open'):
+        return MacOSXEmail()
+    sys.stderr.write("open not found.")
+    return Email()

plyer/platforms/macosx/uniqueid.py

@@ -1,5 +1,6 @@
 from subprocess import Popen, PIPE
 from plyer.facades import UniqueID
+from plyer.utils import whereis_exe
 
 
 class OSXUniqueID(UniqueID):
@@ -17,4 +18,8 @@ def _get_uid(self):
 
 
 def instance():
-    return OSXUniqueID()
+    import sys
+    if whereis_exe('ioreg'):
+        return OSXUniqueID()
+    sys.stderr.write("ioreg not found.")
+    return UniqueID()